To the Op -
I am a measly training level rider and have only been riding a little bit longer than you - 2.5 years. All of the comments here seem to be going completely over your head so I’m gonna give it a shot.
The reason you cannot find free videos to take you to 4th level is NOT because people are withholding information for cash. That’s just silly. It’s impossible. Plain and simple. Since I’ve begun my dressage journey, I’ve spent A LOT of time, not only taking lessons, but WATCHING lessons. We have a GP trainer that comes in several times a year to do clinics, and I do everything I can to be there from the first ride to the last ride, and he may do up to 12 lessons a day.
Every rider is different. Every horse is different. Every rider and horse combination is different. A youtube video cannot tell you that your horse is dropping a shoulder or weak on the left side and what you can do to fix that. A youtube video can’t tell you when you’re crooked in the saddle and leaning to one side. A video can’t tell you when you need to slightly lift your inside rein to correct the bend. You may have 2 horses displaying the same problem, but each horse needs a different approach in how to correct it.
This is what having a good trainer on the ground is for. And when your horse is correct, they will shout at you, “Feel that??” and you know you got it right and now you know the feeling. I don’t care how many books or videos you read, they will NEVER be able to give you that.
Now, I don’t know where you live, but where I live, lessons aren’t $100 across the board. And I may be one of the lucky ones, but I have 2 regular trainers, and our lessons are $35. We have a senior trainer, and she charges $50. Only our GP trainer who flies in for clinics is in the $100 range. No one is going to give you free lessons, but I would think you should be able to find trainers who offer lessons for less than $100.