Advice on cracks in wall and concrete garage floor
DO NOT ignore this issue. The rule of thumb is that if you can get your finger in a crack, it's a problem. You're saying 1cm wide, which is in the problem zone, IMO. 

The cracks might stem from a bad concrete pour. In which case the cracks may have been there since just a few days or weeks after the pour. That certainly possible, and an engineer can tell you if it is.

It's also possible that something is seriously amiss. If so, and you buy the house, then you will be looking for someone to sue when the problem reveals itself more fully. Make sure you have an engineer's report in your pocket when that happens.