Speaking of Russian, I have also learned a little bit, but unfortunately I can only understand what you wrote is "thank you"^^. In fact, when I was learning, vibrato was not difficult for me because I had learned a little Spanish before.

I remember that at that time, I kept practicing, from day to night, without stopping, and I was fine in one day.

First of all, you need to relax your tongue, exhale gently and practice tongue pushing movements. From slow to fast. Move your tongue only once at a time (a trill is formed by rapid vibrations of the tongue many times) and you will hear your tongue make a very soft "t" sound.

After you become proficient, you can exhale forcefully, but still relax your tongue. You will feel it move lightly in your mouth a few times, but your voice will not come out. At this time, you The task is to become proficient until you can make a sound, so that vibrato is enough.

Actually, this is very difficult to teach you, because it relies heavily on feeling, and you have to keep practicing. It doesn’t mean that you continue to practice every day, but that you have to practice every minute and every second. Only when you find the right feeling and express it, can you say you don’t want to practice anymore and continue tomorrow.

PS: If you are not afraid of non-standard, you can start with the "t" or "d" sound, practice vibrato, and then change it later.

You can also consider learning Spanish together to complement each other^^