diff --git a/src/main/java/eu/ztsh/wymiana/service/UserService.java b/src/main/java/eu/ztsh/wymiana/service/UserService.java
index e5b26f6..f9e7cde 100644
--- a/src/main/java/eu/ztsh/wymiana/service/UserService.java
+++ b/src/main/java/eu/ztsh/wymiana/service/UserService.java
@@ -31,7 +31,7 @@ public class UserService {
     }
 
     public User update(User user) {
-        throw new UnsupportedOperationException("Not implemented yet");
+        return UserMapper.entityToPojo(userRepository.save(UserMapper.pojoToEntity(user)));
     }
 
 }
diff --git a/src/main/java/eu/ztsh/wymiana/util/CurrencyMapper.java b/src/main/java/eu/ztsh/wymiana/util/CurrencyMapper.java
index 7542187..b962ddc 100644
--- a/src/main/java/eu/ztsh/wymiana/util/CurrencyMapper.java
+++ b/src/main/java/eu/ztsh/wymiana/util/CurrencyMapper.java
@@ -13,11 +13,19 @@ public class CurrencyMapper {
         return new Currency(entity.getSymbol(), entity.getAmount());
     }
 
+    public static CurrencyEntity pojoToEntity(Currency pojo, String pesel) {
+        return new CurrencyEntity(pesel, pojo.symbol(), pojo.amount());
+    }
+
     public static Map<String, Currency> entitiesToPojoMap(List<CurrencyEntity> values) {
         return values.stream().map(CurrencyMapper::entityToPojo)
             .collect(Collectors.toMap(Currency::symbol, pojo -> pojo));
     }
 
+    public static List<CurrencyEntity> pojoMapToEntities(Map<String, Currency> currencies, String pesel) {
+        return currencies.values().stream().map(entry -> pojoToEntity(entry, pesel)).toList();
+    }
+
     private CurrencyMapper() {
     }
 
diff --git a/src/main/java/eu/ztsh/wymiana/util/UserMapper.java b/src/main/java/eu/ztsh/wymiana/util/UserMapper.java
index b4aff44..39985fb 100644
--- a/src/main/java/eu/ztsh/wymiana/util/UserMapper.java
+++ b/src/main/java/eu/ztsh/wymiana/util/UserMapper.java
@@ -14,6 +14,11 @@ public class UserMapper {
             CurrencyMapper.entitiesToPojoMap(entity.getCurrencies()));
     }
 
+    public static UserEntity pojoToEntity(User pojo) {
+        return new UserEntity(pojo.pesel(), pojo.name(), pojo.surname(),
+            CurrencyMapper.pojoMapToEntities(pojo.currencies(), pojo.pesel()));
+    }
+
     public static UserEntity requestToEntity(UserCreateRequest request) {
         return new UserEntity(request.pesel(), request.name(), request.surname(),
             List.of(new CurrencyEntity(request.pesel(), "PLN", request.pln())));
diff --git a/src/test/java/eu/ztsh/wymiana/EntityCreator.java b/src/test/java/eu/ztsh/wymiana/EntityCreator.java
index df78b20..c0bb186 100644
--- a/src/test/java/eu/ztsh/wymiana/EntityCreator.java
+++ b/src/test/java/eu/ztsh/wymiana/EntityCreator.java
@@ -62,8 +62,8 @@ public class EntityCreator {
         String name;
         String surname;
         String pesel;
-        double pln;
-        double usd;
+        double pln = -1;
+        double usd = -1;
 
         public UserEntityBuilder name(String name) {
             this.name = name;
@@ -93,10 +93,10 @@ public class EntityCreator {
         public UserEntity build() {
             var nonnulPesel = Optional.ofNullable(pesel).orElse(Constants.PESEL);
             List<CurrencyEntity> currencies = new ArrayList<>();
-            if (pln > 0) {
+            if (pln > -1) {
                 currencies.add(new CurrencyEntity(nonnulPesel, "PLN", pln));
             }
-            if (usd > 0) {
+            if (usd > -1) {
                 currencies.add(new CurrencyEntity(nonnulPesel, "USD", usd));
             }
             if (currencies.isEmpty()) {
diff --git a/src/test/java/eu/ztsh/wymiana/service/CurrencyServiceTest.java b/src/test/java/eu/ztsh/wymiana/service/CurrencyServiceTest.java
index cc640a0..95b1442 100644
--- a/src/test/java/eu/ztsh/wymiana/service/CurrencyServiceTest.java
+++ b/src/test/java/eu/ztsh/wymiana/service/CurrencyServiceTest.java
@@ -69,7 +69,7 @@ class CurrencyServiceTest extends RepositoryBasedTest {
     @Transactional
     @Test
     void usdToPlnToSellSuccessTest() {
-        var entity = EntityCreator.user().pln(0).usd(USD_SELL).build();
+        var entity = EntityCreator.user().pln(-1).usd(USD_SELL).build();
         userRepository.save(entity);
         var result = currencyService.exchange(EntityCreator.exchangeRequest()
             .from(USD_SYMBOL)
@@ -85,7 +85,7 @@ class CurrencyServiceTest extends RepositoryBasedTest {
     @Transactional
     @Test
     void usdToPlnToBuySuccessTest() {
-        var entity = EntityCreator.user().pln(0).usd(USD_SELL).build();
+        var entity = EntityCreator.user().pln(-1).usd(USD_SELL).build();
         userRepository.save(entity);
         var result = currencyService.exchange(EntityCreator.exchangeRequest()
             .from(USD_SYMBOL)
diff --git a/src/test/java/eu/ztsh/wymiana/util/UserMapperTest.java b/src/test/java/eu/ztsh/wymiana/util/UserMapperTest.java
index 0479332..0b4a7d9 100644
--- a/src/test/java/eu/ztsh/wymiana/util/UserMapperTest.java
+++ b/src/test/java/eu/ztsh/wymiana/util/UserMapperTest.java
@@ -25,6 +25,20 @@ class UserMapperTest {
                 .isEqualTo(expected);
     }
 
+    @Test
+    void pojoToEntityTest() {
+        var entity = new User(
+                EntityCreator.Constants.NAME,
+                EntityCreator.Constants.SURNAME,
+                EntityCreator.Constants.PESEL,
+                Map.of("PLN", new Currency("PLN", EntityCreator.Constants.PLN))
+        );
+        var expected = EntityCreator.user().build();
+        assertThat(UserMapper.pojoToEntity(entity))
+                .usingRecursiveComparison()
+                .isEqualTo(expected);
+    }
+
     @Test
     void requestToEntityTest() {
         var request = EntityCreator.userRequest().build();