C++ budgeting application

Link to the project on GitHub:

Below I present photos that showcase the application's most important features.

Starting view - main menu
New user registration.

All entered data must not contain Polish characters.
Log in for registered user. The user has 3 attempts to enter the correct password. After 3 failed attempts, they will be redirected to the "Home Menu".
After logging in, "Main Menu" appears.
Add revenue.
Adding an expense.
Displaying the current month's balance.
Displaying the previous month's balance.

Please note here that fractional amounts are written using a full stop (.). Even if the user enters an amount with a comma, it is changed to a full stop.
Displaying the balance for any chosen period of time.
Finally, change the password.