Are there any courses on (stock) investing that are worth paying for?
Generally, no there are no courses worth paying for. Almost everything in the retail trading space is either too general to be of use (vague advice like “let your profits run and cut your losses short”), outright scammy (like the answer below, “be an expert in 15 days”), not based on actual empirical evidence (like approximately 80% of technical analysis which resembles astrology more than an actual trading strategy).
The truth is that you can get every bit of information you need from books, in a lot more detail than the “introduction to losing your money” courses.
I generally advise people to start with Alexander Elder and Van Tharp’s books, and move to more advanced things from there. Neither has enough to really trade with, but there is enough info to decide if you want to go deeper.
What do you need to do?
You need to build a trading system, that suits your market beliefs, personality and financial goals, and trade that system without error, keeping detailed records and making constant refinements.
This is a big ask, and will take you some time. But a smart beginner will break this huge task down into bite sized chunks and get chewing.
If you do insist on paying for seminars and courses, some of Van Tharp’s are actually excellent, some are beginner level garbage, but all of them are a rehash of what is in his books at 500x the price. His “super trader” course at a cost of $50,000 or so actually has a good track record of turning out professional traders, but there is literally nothing in there that a motivated person could not figure out. Some years ago I did his “building trading systems” course and found it useful, but way too basic and beginner oriented to be of practical use. I had to do a lot of self-learning to figure the rest out, and along the way I realised there were some pretty bad assumptions being made.