I downloaded it from jenkins when i try to join server with 1.15.2 it says outdated server and when i use 1.15.1 it says please use 1.15.2 what the heck ??
You can't use older versions on current versions = you can't use 1.15.1 on 1.15.2. You need to either update your Minecraft (recommended) or install ProtocolSupport (not recommended).