My situation is a bit unusual: I plan to apply for a second Master's degree in a foreign university I did an exchange semester in. It is pretty well-ranked compared to my current one. The Master's is related to my current one, but contains more theory (from a computer science degree with data science courses to a machine learning degree).
I need two letters of recommendation, and I am thinking about asking professors whose courses I followed during my exchange semester. Since my application is borderline (good grades lately, less so in my first two years of bachelor's) and the program is competitive, I assume that a letter of recommendation from professors at the same university would give my application a much-needed boost, especially since they teach courses in the program I am applying to.
I don't know how to ask for letters. I have never done it, and while I passed these courses, I didn't have the kind of stellar results that would make them call me a genius in the letter, though I think that they would be willing to help if I asked.
Is a good letter from my current university a better bet than an okay one from the university I apply to? Should I send one letter from my current uni, and one from the one I want? Is it even a good idea to ask these teachers for letters if I didn't have a close working relationship with them? If so, how would I go about asking them for a letter?