this tree has been struggling for years,tho still makes fruits (less and less as years pass) whats left to do?? (Golden Drop plum)

I don’t know much about it .. although i noticed some fungi and what looks like webs ?(mold, still pretty much uncertain ) and there’s also some holes and

it used to be filled with ants, i dont see many anymore at the moment.

Is there anything i can do to helpt? otherthan just planting a new one..

I really lowk wanted to try some ctreatments but i still dont knowwhat to do, any tip will be appreciated.