我就在原文上改动了哦~
f I were a father
We all must be fathers or mothers in the future.（这句我会说成：we all will become parents in the future）If I were a father,how should I treat my kids?Here is my idea.
If I were a father I would teach my kid a lot （加 of,a lot of）truth.For example,I would teach my kid to be happy all the time,to reagrd difficulty as challenge,to beat(我不确定beat有这种用法,用solve/work out来表示解决困难吧,或者用overcome更好) all the problems……If I were a father I would make friends with my kid.I would play games with it(你这里所有的it 都换成him吧,“他”而不是“它”),I would keep it healthy,and （加上make him）grow fast.If I were a father ,I wouldn't make it get so good grades,but it is not allowed to copy others.（你是想表达,我不会要求他有很好的成绩,但是他决不允许抄袭对吗?那就说,I wouldn't require him to get very good grades,but he shouldn't be allowed to copy others' papers or homework.）Also I would help it to make a lots(lot,a lot of 去掉s) of friends.
I believe if I were a father ,I would be （a very good one).
以上就是我的改动,没有改动你的句型什么的,还是你自己的风格