1) When we use “seem(s) to,” it does not refer to the future: it means that we have looked
at something and seen how it looks in the present. What you want to say here is the
future--”When I go to sleep, I think I will be able to sleep well.” That’s one possible
phrasing, and I’ve offered another, “I should be able to sleep well.” You could also say
“I’ll probably sleep well” or “I expect to sleep well,” among others.
2) In order not to begin two sentences in a row with “because,” I took it out here and
changed the sentence to use “so.” The meaning is the same.