Slow computer

I am asking myself why is my computer running slow and I can't seem to find the proper answer. However, when I think again, I don't really care why my computer is running slow, I just want to fix it. That is all I want. I asked my brother for help and he told me about this YouTube video. He told me to watch it and said that it would fix my problem. I am going to watch it this evening and hopefully, I will watch my favorite series tonight without restarting everything. My brother was really convincing and I hope that he is right about this video.