I chose the wrong choice...,

[Silverobama]

My friend was doing his livestream on social media and I was watching. Suddenly a question popped up on the screen, the question was "Do you think this is an ad?" It means that "Do you think the person who does livestreaming is advertising" and I mistakenly pressed the button "yes"! Then I said to my friend:

Sorry, Richard, a question asked me if you were an advert and I pressed the "yes" button.

I think "pressed the button" is weird but I don't know what to say; there's no button at all to press but some choices to pick.

Please help me with a natural version.

 

[Skrej]

A few options (there are many more):

I hit/pressed/clicked/selected 'yes' by accident.
I accidentally hit/pressed/selected 'yes'.
I mistakenly hit the 'yes' button.

We still call it a button even if it's technically just a graphic on the screen. It's optional anyway in my last example, although if you omit it, you need to also omit the definite article.

In programming, these are in fact called 'radio buttons':

 

[emsr2d2]

Yesterday/This morning/Recently, I was watching my friend was doing his livestream on social media. and I was watching. Suddenly a question popped up on the screen. The question was "Do you think this is an ad? Yes/No". It means meant that "Do you think the person who does is livestreaming is advertising" and I mistakenly pressed the button "Yes"! Then I said to my friend:

Note my changes above. Your opening sentence would be much more natural with some kind of time marker. You had a comma splice ("up on the screen, the question was"). I added "Yes/No" because if the screen that popped up simply said "Do you think this is an ad?" without any answer options, it would have been pointless. You didn't need "the button" at all, even though generally the bit you click on is called a button!

Sorry, Richard. During your livestream, a question popped up on screen asking me if you were an advert advertising something and I pressed the "Yes". button.

See above. You needed more information in that part. Saying "Sorry, Richard. A question asked me" wasn't just ungrammatical; it wouldn't have given Richard enough information.

I think "pressed the button" is weird but I don't know what to say; there's no button at all to press but some choices to pick.

As long as the options actually appeared on screen and you had to click one of them, it's fine to call it a button. However, you didn't need it. You can just say "I pressed/clicked Yes".