Math-Math trilinear algebra is almost as difficult. In fact, it is difficult to say that linear algebra is difficult, mainly to lay a good foundation. No matter whether your foundation is good or bad, you need to read books. If you have time, do exercises after class. No, look at the answer. Then make a review book. I won't review the whole book, so I need to return to the textbook. The textbook may need to be read several times.