diff --git a/src/data/enums/country.rs b/src/data/enums/country.rs
index 3f6b1e4..7ad3969 100644
--- a/src/data/enums/country.rs
+++ b/src/data/enums/country.rs
@@ -1,13 +1,13 @@
-use crate::enums::errors::internal::{CountryError, InternalError};
 use diesel::{
     deserialize::{self, FromSql, FromSqlRow},
     expression::AsExpression,
     pg::{Pg, PgValue},
     serialize::{self, IsNull, Output, ToSql},
 };
+use serde::{Deserialize, Serialize};
 use std::io::Write;
 
-#[derive(Debug, AsExpression, FromSqlRow, PartialEq, Eq, Clone, Copy)]
+#[derive(Debug, AsExpression, FromSqlRow, PartialEq, Eq, Clone, Copy, Serialize, Deserialize)]
 #[diesel(sql_type = crate::data::schema::sql_types::Country)]
 #[allow(clippy::upper_case_acronyms)]
 pub enum Country {
@@ -16,17 +16,6 @@ pub enum Country {
     Germany,
 }
 
-impl Country {
-    pub fn from_str(s: &str) -> Result<Country, InternalError> {
-        match s {
-            "UK" => Ok(Country::UK),
-            "USA" => Ok(Country::USA),
-            "Germany" => Ok(Country::Germany),
-            _ => Err(InternalError::CountryError(CountryError::CountryNotFound)),
-        }
-    }
-}
-
 impl ToSql<crate::data::schema::sql_types::Country, Pg> for Country {
     fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> serialize::Result {
         match *self {
diff --git a/src/data/enums/oauth_provider.rs b/src/data/enums/oauth_provider.rs
index 59f00d6..baeb380 100644
--- a/src/data/enums/oauth_provider.rs
+++ b/src/data/enums/oauth_provider.rs
@@ -7,8 +7,6 @@ use diesel::{
 use serde::{Deserialize, Serialize};
 use std::io::Write;
 
-use crate::enums::errors::internal::{AuthError, InternalError};
-
 #[derive(Debug, AsExpression, FromSqlRow, PartialEq, Eq, Clone, Copy, Serialize, Deserialize)]
 #[diesel(sql_type = crate::data::schema::sql_types::OAuthProvider)]
 pub enum OAuthProvider {
@@ -17,17 +15,6 @@ pub enum OAuthProvider {
     Discord,
 }
 
-impl OAuthProvider {
-    pub fn from_str(s: &str) -> Result<Self, InternalError> {
-        match s {
-            "Github" => Ok(OAuthProvider::Github),
-            "Google" => Ok(OAuthProvider::Google),
-            "Discord" => Ok(OAuthProvider::Discord),
-            _ => Err(InternalError::AuthError(AuthError::UnknownOAuthProvider)),
-        }
-    }
-}
-
 impl ToSql<crate::data::schema::sql_types::OAuthProvider, Pg> for OAuthProvider {
     fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> serialize::Result {
         match *self {
diff --git a/src/data/enums/os.rs b/src/data/enums/os.rs
index d11c78b..40a9232 100644
--- a/src/data/enums/os.rs
+++ b/src/data/enums/os.rs
@@ -27,19 +27,6 @@ pub enum OS {
     Unknown,
 }
 
-impl OS {
-    pub fn from_str(s: &str) -> Self {
-        match s {
-            "Windows" => OS::Windows,
-            "Linux" => OS::Linux,
-            "MacOS" => OS::MacOS,
-            "Android" => OS::Android,
-            "IOS" => OS::IOS,
-            _ => OS::Unknown,
-        }
-    }
-}
-
 impl ToSql<crate::data::schema::sql_types::Os, Pg> for OS {
     fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> serialize::Result {
         match *self {
diff --git a/src/dto/auth/request/authorize.rs b/src/dto/auth/request/authorize.rs
index 34f8e44..dfb62c5 100644
--- a/src/dto/auth/request/authorize.rs
+++ b/src/dto/auth/request/authorize.rs
@@ -1,10 +1,10 @@
-use crate::dto::device::internal::DeviceInfo;
+use crate::{data::enums::OAuthProvider, dto::device::internal::DeviceInfo};
 use serde::{Deserialize, Serialize};
 use utoipa::ToSchema;
 
 #[derive(Debug, Serialize, Deserialize, Clone, ToSchema)]
 pub struct AuthorizeRequest {
     pub code: String,
-    pub provider: String,
+    pub provider: OAuthProvider,
     pub device: DeviceInfo,
 }
diff --git a/src/dto/device/internal/device_info.rs b/src/dto/device/internal/device_info.rs
index cfe4ad2..47cf345 100644
--- a/src/dto/device/internal/device_info.rs
+++ b/src/dto/device/internal/device_info.rs
@@ -1,10 +1,11 @@
 use serde::{Deserialize, Serialize};
 use utoipa::ToSchema;
+use crate::data::enums::OS;
 
 #[derive(Debug, Serialize, Deserialize, ToSchema, Clone)]
 pub struct DeviceInfo {
     #[schema(example = "Android")]
-    pub os: String,
+    pub os: OS,
     #[schema(example = "Vitya Phone")]
     pub name: String,
 }
diff --git a/src/dto/session/request/create_session.rs b/src/dto/session/request/create_session.rs
index c8ee9d9..7e79023 100644
--- a/src/dto/session/request/create_session.rs
+++ b/src/dto/session/request/create_session.rs
@@ -1,7 +1,8 @@
+use crate::data::enums::Country;
 use serde::{Deserialize, Serialize};
 use utoipa::ToSchema;
 
 #[derive(Debug, Serialize, Deserialize, ToSchema, Clone)]
 pub struct CreateSession {
-    pub country: String,
+    pub country: Country,
 }
diff --git a/src/handlers/auth/authorize.rs b/src/handlers/auth/authorize.rs
index b8b9aa7..963c8af 100644
--- a/src/handlers/auth/authorize.rs
+++ b/src/handlers/auth/authorize.rs
@@ -1,5 +1,4 @@
 use crate::{
-    data::enums::OAuthProvider,
     dto::{
         auth::{internal::OAuthCode, request::AuthorizeRequest, response::Tokens},
         device::internal::DeviceInfo,
@@ -21,7 +20,7 @@ pub async fn authorize(
         &state,
         &OAuthCode {
             code: payload.code.clone(),
-            provider: OAuthProvider::from_str(&payload.provider)?,
+            provider: payload.provider,
         },
         &DeviceInfo {
             os: payload.device.os,
diff --git a/src/handlers/session/create_session.rs b/src/handlers/session/create_session.rs
index 7531c3d..ac9f5d9 100644
--- a/src/handlers/session/create_session.rs
+++ b/src/handlers/session/create_session.rs
@@ -1,5 +1,4 @@
 use crate::{
-    data::enums::Country,
     dto::{
         auth::internal::AccessToken,
         response::success::Response,
@@ -61,8 +60,7 @@ pub async fn create_session(
     State(pool): State<Pool>,
     Json(payload): Json<CreateSession>,
 ) -> Result<Response<Session>, ExternalError> {
-    let country = Country::from_str(&payload.country)?;
-    let session = session_service::create_session(&pool, &claims.device_id, &country).await?;
+    let session = session_service::create_session(&pool, &claims.device_id, &payload.country).await?;
 
     info!("Session created successfully: {}", session.session_id);
 
diff --git a/src/services/user_service.rs b/src/services/user_service.rs
index 0de7bde..0d294ca 100644
--- a/src/services/user_service.rs
+++ b/src/services/user_service.rs
@@ -249,7 +249,7 @@ pub async fn sign_in(
 
     let device = NewDevice {
         name: device.name.clone(),
-        os: OS::from_str(&device.os),
+        os: device.os,
         user_id: user_db.user.id,
     };
     let device = device_service::add_device(pool, &device).await?;
@@ -297,7 +297,7 @@ pub async fn sign_up(
 
     let device = NewDevice {
         name: device.name.clone(),
-        os: OS::from_str(&device.os),
+        os: device.os,
         user_id: current_user.user.id,
     };
 
@@ -335,7 +335,7 @@ pub async fn authorize(
 
     let device = NewDevice {
         name: device.name.clone(),
-        os: OS::from_str(&device.os),
+        os: device.os,
         user_id: user.user.id,
     };