I started off and gained one master by building and fixing the first 2 buildings and then the dam and the thorns but I didn't realise at the time I'd need more than one, by the time I realised my one master was ready for popping his clogs and it was too late to get others up to speed, which is why I think I'm going to have to start again lol
I'm hoping the last 2 puzzles might help and am furiously racking up tech points so I can get my culture and exploration level 3. Wish me luck