Swimming lesson for adult in tainan who can speak english
Maybe go to any swimming pool and ask. This is what I would recommend in Taipei. The instructor’s English doesn’t need to be perfect unless maybe you are a good swimmer and you need to tweak things here and there.
Edit: From your name I guess you are female? You might want to find a female instructor so that she can physically show you how to kick better, pull your arms, etc.
Do not know if Tainan has YMCA, but Taipei does and has both male and female swim instructors for (mostly) children. Guessing you could ask about one-on-one lessons.
Also, try going to the big universities in town. They generally have open swim-hours to the public and if you get the right school, you’ll have PE students teaching kids and adults (like at NTNU in Taipei and NKNU in Kaohsiung; can confirm both personally).
You just have to ask at the check-in counter.
The college students’ English is typical good enough for basic instructions.