Wanting a raise but am confused with the situation

So I’ve worked at this company 3 separate times, once in highschool in the position (I’m in right now), after I graduated I was in a different division for a year before being laid off, and now I’m in the shop as a labour (same as in highschool). I just hit my three months and was going to ask for a raise sooner, but unfortunately, was too busy to find time for it. I show up on time ready to work, I’m reliable on showing up, I help out the team whenever needed regardless of who asks, and I produce more than the given daily personal quota. I’ve asked to learn more multiple times, but always given the same answer of “when we’re less busy” or no reply at all, and it sucks all the same each time. A couple days ago I was told that I would be taught how to operate one of the machines which I would definitely want to do, however, I would be doing split night shifts. While there is a five dollar incentive for nights, as well as an increase of two dollars once I’m fully trained in about a month. To me it kind of feels like the last three months were absolutely nothing then, like I definitely appreciate a raise for once I’m trained. However given that a lot of people at the company get raises after their three months, and the work I prove that I’m capable of I thought it was a given. However, I believe that there was some miscommunication between my manager and I since his response was “ You’ll get an increase after your training.”. My other issue with the night shift is that it would be only myself and one other person working. I sent him a list of questions that I had including what happens if that other person calls in sick or is a no-show, do I end up losing hours then give that I can’t work alone? However, a day later, I still don’t have any answers, yet I’m expected to give him an answer tomorrow morning. I’ve been incredibly stressed out throughout the last couple days and definitely need some advice on this.