SOMEONE HELP PLEASE:( I'm getting a new bike and i'm wondering if a Shimano TX50 front derailleur is good enough and will do the job or should I get another bike which has an acera, FD-M390 front derailleur. Thanks in advance for ur help!
Front derailleur is not a particularly important component to optimise, in my opinion, since it only touches the chain when being operated (assuming it is correctly set up so the chain doesn't rub). I doubt Shimano sells any derailleurs that don't "do the job" of shifting gears, so at worst the shifting in the front will be a bit worse and the components will weigh a bit more.

You can also switch the derailleur later, and especially the front ones are not particularly expensive (in fact both of the ones you mentioned are such low-end ones that it would make little sense to buy either separately).

So, choose the bike that has the nicest frame, fit, and feel for you. Replace individual components later if you are not happy with some of them.