Tip of my Tongue: To do something one headed
This is also reflected in the language. One expression I found particularly funny upon first (and consecutive) hearing is: tek başına yapmak. It translates into “to do something one headed” (literal) or “doing something by oneself” (figuratively speaking).
Whenever I hear this expression, I can’t help but think of a multi-headed creature with only one head remaining doing this or the other activity. Doing something “one-headed” is actually something rare in Turkey as you will generally see groups of people rather than individuals, so doing something “multiple-headed” would be the most common case.