It is true that a new decree was issued that if you have served 1.5 years, you can leave...?

There is such a bill under number 9142 (https://itd.rada.gov.ua/billInfo/Bills/Card/41635), but it has not yet been adopted.

According to the above draft law, citizens who undergo military service and have been mobilized since the introduction of martial law have the right to serve no more than 18 months from the moment of conscription, if they have not expressed a desire to continue military service.