I believe you have difficulty in doing these.

我相信你做这些是没有困难的。

When I have difficulty in doing anything, I will ask my father for advice.

每当我做事遇到困难时，我往往向我父亲求教。

Some students have a lot of difficulty (in) doing math problems.

一些学生做数学题有很大困难。

B have difficulty(in)doing sth.

“做……有困难”，固定用法。

If you follow my advice, you will have no difficulty in doing these things.

你如果听从我的意见的话，你做这些事情是没有困难的。