i think it would help if you included the rest of the sentence! but this is a very complicated way of saying something like: The problems are caused by a factor that (from the very beginning) made it seem that things weren't going to work out.

Hi David, The test was really hard for me > Para mí el examen estuvo dificil. (correct) "for me" expresses your opinion "to me" is more like "a mi" and wouldn't make sense unless you said something like "The test SEEMED really hard to me" Other examples: The tacos were too spicy for me. Today was too hot for me. She spoke really fast for me. (Here, "to me" would just be a fact that she was speaking to you quickly, and "for me" means that you had a hard time understanding)

If you need to tell them you have to go, you can say something like: I have to get back to work, but let's catch up more later! (Or Let's talk more later - I gotta go for now!) Or just "Okay Linsey, I gotta run. Talk to you again soon!"

We need to resolve the problem by Monday. We need to keep trying to resolve the problem until Monday. Until implies that something that is happening will end on precisely on Monday. By implies that something that hasn't happened needs to happen anytime before Monday. Another example: He will be finished with his project by next week. He will be busy working on his project until next week.