all tasks are solved

src/main/java/mate/academy/service/AuthenticationService.java

@@ -1,5 +1,7 @@
 package mate.academy.service;
 
+import mate.academy.model.User;
+
 public class AuthenticationService {
     /**
      * Imagine that some user wants to login to your site.
@@ -11,6 +13,17 @@ public class AuthenticationService {
      * Return false in any other cases.
      */
     public boolean login(String email, String password) {
-        return false;
+        UserService newUserSerice = new UserService();
+        User user1 = newUserSerice.findByEmail(email);
+        if (user1 == null) {
+            return false;
+        } else {
+            String correctPassword = user1.getPassword();
+            if (password.equals(correctPassword)) {
+                return true;
+            } else {
+                return false;
+            }
+        }
     }
 }

src/main/java/mate/academy/service/UserService.java

@@ -15,6 +15,11 @@ public class UserService {
      * Return <code>null</code> if there is no suitable user
      */
     public User findByEmail(String email) {
+        for (User element: users) {
+            if (email.equals(element.getEmail())) {
+                return element;
+            }
+        }
         return null;
     }
 }