How long should I wait before doing bodybuilding exercises after hair transplant? What happens if I do bodybuilding exercises ?

It is best to ask your surgeon about post operative care as each doctor has their unique regimen.  Most doctors would tell you to take it easy for a few weeks.  The Internet will only slow you down with possibly conflicting information 

This is a question maybe every surgeon or expert will answer different but we recommend our patients to start will low exercises after 15 days and with strong activities after 1 month. Please consult with your expert as he may has other advises to you.

That's a question every doctor will answer differently, but the general consensus is waiting 1-2 weeks, occasionally more, before resuming strenuous activities such as bodybuilding. Your best bet would be to ask your own doctor, as they know the specifics of your case.