I have been struggling for a while with these mental exercises, I really need help. I'm hoping that I'll find some rare individuals with key knowledge on this niche website.

Please read carefully and answer the three questions to best of your abilities. Thank you for the help.

If you don't have an answer for #2 but you are actually proficient at #1 then that's good too, I can't move on to exercise #2 anyways because I'm stuck at a 1 minute duration for #1.

Questions:
1. Have you practiced Dharana (concentrating on a single thought for a prolonged period without ANY mental interruptions), and how long can you last (in minutes)?

2. Have you practiced Dhyana (emptying the mind of all thoughts for a prolonged period without ANY mental interruptions), and how long can you last (in minutes)?

3. What kind of specific training/method did you use to attain your level of proficiency in both exercises (book, course, etc)? - Be as specific as possible