Plenty of people learn good form/mechanics from watching videos, and only use a trainer when they run into a real stumbling block.
If you’re having trouble with any of these, the advice is to still record yourself doing a lift and seeing where you go wrong, as people’s proprioception isn’t always as good as they think it is, especially when learning a new skill on their own.
We’ve also compiled Megathreads of commonly recommended instructional videos for the most common lifts on our Learning and Improving Lifts page. ExRx.net’s exercise pages can also be a great resource, as well as a simple YouTube search.
Also, we have a semi-regular Instructional Video Megathread that you can check out.