Tread cautiously. I experienced some issues achieving an erection and feeling stimulation after several days on it. Needless to say I stopped after two weeks. Fortunately I didn't experience any permanent side effects. It's too bad; I really wanted to stop the full front assault!
I was on it for maybe 2 weeks. A few days in I noticed a sort of numbing of my weenie. Needless to say I stopped taking it shortly thereafter and things went back to normal. I don't want to know what would've happened had I continued for a long duration.
Reminded me of a video that depicts thousands of African tribesman and their dogs on a mass hunt. It's awful to watch but it gives you an idea of how our ancestors hunted thousands and tens of thousands of years ago.
I used Khan Academy for 2-3 months while I had a full-time job. I worked my way up from College Algebra to Calculus I before I took community college courses in Calculus I and Calculus II. It definitely prepared me for the college courses.
I made the same moves last year and have no regrets. I was 28 when I quit my career in finance in May 2017. It's definitely been the hardest thing I've ever done (System's Architecture and Computer Networks) but it's been the most rewarding. I'll be finishing Year 1 of 3 this June.