I would appreciate if you can help with me the problem

I would appreciate if you can help with me the problem
I would appreciate ____if you can help with me the problem
这里为什么用it
___many times,but he still couldn't understand.
这里前面是不是因为后面有but,所以不能用though……
it seems hard to believe ___is now an international sport came from a simple game in the 16th century.
这里为什么用that what 而不直接用what 或者that
____Mike failed again in the test made his teacher disappointed.
这里为什么用that而不能省略.