Hi Niklas, I think there are two reasons people say steel string acoustic guitars are “painful” to play. First: the steel strings (especially the first three - the skinny ones) are, well, made of steel. It takes a few weeks to build up callouses, but we all do it. And you will too. The second reason is that the acoustic guitars tend to use thicker strings than electric guitars, and the tension is higher. This means the strings are a bit more difficult to depress than strings on an electric. Notice that none of this has anything to do with your elbow! Edit to correct: As @Tbushell points out, this is not accurate. Still, I think Niklas can probably manage a change to a steel-string acoustic if he gets one that fits him well.
That said: Make sure you try out guitars before you buy one. As you narrow down body styles, be sure to spend a significant amount of time (I’d suggest at least 20 minutes) playing an instrument to determine if it will be comfortable. You’ll see many, many people buy a dreadnaught guitar as their first instrument, only to find out it is too large for them. Especially for beginners, having a guitar that is not comfortable to play can cause elbow pain, shoulder pain, wrist pain. Here’s a thread discussing “smaller” guitar bodies I started a while back…people shared a lot of good information in it!
Let us know how your shopping goes!