Pfizer Testosterone

I'd love to hear about your experiences with this. Also, what's the best way to take it, and are there any specific things I should watch out for? Thanks so much!

This inquiry is specifically intended for an endocrinologist, assuming one is actually facing a legitimate medical issue—that is to say, a clinically proven deficiency or some specific physiological condition that requires professional intervention.
If you are merely looking at this from a recreational standpoint, then again, you really ought to have a qualified specialist design your protocol, rather than relying on the unsolicited advice of some random gym rat on a message board.

So, I’m looking at this from a sports perspective—specifically focusing on building muscle mass. Does anyone happen to know a solid professional in this field? Or better yet, does anyone have tips on where I can actually track down someone truly qualified? 😁

You might want to check out the PDF on fitness training 🤷
Alternatively, you could just log onto a dedicated bodybuilding forum and see if anyone there can point you toward a reputable expert.
Just please, for your own sake, be extremely careful about low-quality supplements and people who clearly don't know what they're talking about.
Since you’ve already decided to take this particular path, I suppose there isn't much stopping you.
But honestly, if I were you, I wouldn't meddle with this any further 🙂

I'm in complete agreement with the points made above.

That's the key.