>>1301025>not mine but same modelfirstly post some good photos of your actual bike.
Secondly, it's probably not cost effective, as you'll need new wheels to change to a modern system, a new crank, new everything really. You can definitely upgrade and service it piecemeal though. One option is to find a good local source for quality used parts or get a donor bike.
A new altus derailleur would work.
Maybe also look out for just a higher quality old mtb if you want a project (something stock with deore or xt on it), although that one is probably still good and if you like it and it fits you that matters more.
Buying a complete new group? No. Get a new bike instead.
