Hi there! I'm new to the site and the sport as well! I'm from Greece and about a month ago i remembered my old bike..

an old crapy mountain bike. I live near forest so i thought it'd be a good idea for me to start biking in the trails of the forest. The thing is that after about 4 times today my rear wheel curved (so it couldn't move). I searched the internet for wheels and other parts for my bike and i also checked for a whole new bike. So i wondered if its better to "fix" my old bike putting some new parts as wheels and brakes or to buy a new one (that will cost no more than 400-500 euros)

well if you describe your old bike as "crappy" then i guess you should buy a new one. is it really that old to be called crappy? and if money isn't an issue, then go ahead and buy yourself a new one. i assume your money won't go to waste since you said that you live near a forest, you'll be using it frequently