**Neither a teacher nor a native speaker.**
Maybe it's more difficult than I think, but I will try to help you anyway.
Until -> future
Since -> past
1. I have been correcting some tests since 10:00 am today.
2. I will correct some tests until 10:00 am tomorrow.
1. You have been doing this (it started in past - 10:00 am today - and it is still active).
2. You will do something until a specific moment (tomorrow 10:00 am).
I'm not 100% sure if I actually figured out the problem...
And probably you don't need the "will" in sentence 2.
My examples do not fully match your sentence, but yours should be:
"I have to correct some tests until/
Student or Learner