Romet Mustang 29 1.0?
 

hey im im looking to buy new bike i want to ask question :)

is this bike good worth buying ?

MUSTANG 29 1.0 - MTB - Romet

I don't know what the bike market is like in Poland, so I can't tell you if the bike is a good one for the price. I don't know what kind of riding you plan on doing, so it's hard to say if that bike is a good one for how you want to ride.

I do know, however, that this particular forum is for "classic and vintage" (old) bikes, and we're probably not the best group of folks to answer this particular question. You might want to try the mountain bike forum.