There is not a whole lot to be done at this point. It would seem possibly that some other funds have been acquired and consolidated into this address:
via this txn, which is connected to your balance / address:
But there is not any identifying information there and it could be in anyone’s hands. Without the help of law enforcement agencies and cyber forensics there isn’t much that can be done about things like this. If stolen crypto goes to an exchange address you can try to appeal to them and maybe something will be done about it, but don’t hold your breath.
In regards to what you “should do”, if you are not sure whether your setup is secure i.e. you do not have experience dealing with computer or network security issues, you should most certainly be using a hardware wallet device if you cannot afford to lose your investment.
Unfortunately that is all I can offer you at this point.