Every time I try to make a foundation it has a melt down.

So my mother and I are trying to build her first home on the game. I have tried at least 10 times to make a simple foundation and everytime I get it to go up, something happens and I can’t add flooring, foundation decor, nothing. I go to put it back down, nada. I try reversing no, I try going in and out of build mode to see if that helps, NOPE! then I try to save it and I won’t loud my saves list, I even try to go back to the main menu and it gets stuck in freeze mode and won’t load. So I have to hard quit the game, iv tried everything but uninstalling and reinstalling cuz I made every person perfectly and that took me at least 4 hrs of game play alone xc. Plz help!