There are few solutions online for Schwartz. No solution manual exists, as far as I found. Answers to the first 7 sections in the first part of the book can be found here: https://ytcs.github.io/schwartz.pdf. These solutions aren't very pedagogical at all, and so it may take a while to figure out some of the steps the author has taken, but it is useful for telling you what you need to be thinking about.

I have found with Schwartz that you can come on to Physics SE or search on Google and, after a while digging through posts, find solutions to most of the questions, or at least good hints or partial solutions. This requires a bit of searching, but because a lot textbook exercises are standard derivations they have not had the space to include in the main text, or rehashed exercises from older books, you can usually find what you need online.