Is COGO compatible with LEGO sets, that is can I combine parts from both packages? My kid got a COGO set on his birthday recently, which we did not open because I think we can return and exchange (for a surcharge) it at toy store where it was bought, if they can not be used together with LEGO bricks that is.
Welcome! COGO is a clone brand, and hence not generally used around here. COGO bricks will work with LEGO, however, the quality, finish and fit of COGO bricks is significantly less than LEGO's, so I would advise to return the COGO set and buy a (smaller but) better quality LEGO set instead.
Yes COGO are compatible with LEGO. And I wonder why we don't find them easily - I love them. And it works great for missing LEGO peices.