How can I scroll with selenium if I already follow a user?

This part of your code does not make sense:

buttons = driver.find_element_by_xpath("//*[text()='Follow']")    
scroll = 0
sleep(10)
fBody  = driver.find_element_by_xpath("//div[@class='isgrP']")   
for btn in buttons:
     if btn.text == 'Follow':
         driver.execute_script("arguments[0].click();", btn)
         sleep(60)
     else :
         driver.execute_script('arguments[0].scrollTop = arguments[0].scrollTop + arguments[0].offsetHeight;', fBody)

Please be aware, that first you are getting all elements with text 'Follow' to buttons, then you check if text of each element is in fact equal to Follow. Try to find different locator for those buttons, e.g.

//div[@aria-label='Followers']//ul//button

with this, you will get list of buttons (with and without 'Follow' text), then you can perform your actions depending if text equals 'Follow'.