I may have replaced my serpentine belt/alternator incorrectly

I recently replaced the serpentine belt on my car listed above hatchback. The belt replacement was done with a new friend who has some good experience. When replacing the belt, I placed a mark on the sliding bar connecting to the alternator to show where the pulley for the belt was lined up before. When he finished pulling the alternator back into place, it was far above the mark implying the belt would be loose. I asked about it and he said the tension was fine.

When I got back into my car I didn't have an issue for 2 days. After two days passed the car started to screech on start up. As the next two days passed the screeching even occurred if I stopped while idling the engine and would screech until I accelerated to a certain speed. Around that same time, the moment I start up the car, the green engine temperature light would turn on for about 15-45 seconds. I know that the coolant pump is related to that belt on my car. I'm hoping I should just go tighten the belt, but I'm not sure that will fix the issue with the coolant light going on for a few minutes.

I learned a lot from the guy who helped me, but I'm not very knowledgeable when it comes to cars. I could really use some help because I'm a bit broke at the moment and there is still more to be done in the future that I need to save for. I would really appreciate any information you could provide.

Thank you for your time and consideration.


- Devin F.