Hi flower
im not going to add to the above advice as it is correct, im just posting to say how sorry I am that your first attempt at tiling went so wrong for you
persever with this and redo it and you will have a job that you and your parents will be proud of
Can't say more than that. It goes to show how important adhesive selection is. And how important it is to use a dedicated tile forum to find out what adhesive to use too