Illustrator: Unable to scale any objects

Hi!

I work with Illustrator for a while now but I'm still kind of a beginner. So yesterday suddenly a problem accured and I wasn't able to fix it, maybe you can help me.

So normally, when I dial an object or text field, the frame gets these little white boxes in the corners with which you can scale the object (when moving the cursor over the corners there will accure a little arrow, I hope you know what I mean). I don't know why, but when I dial an object now, the corners don't change (they stay in the colour of the frame and when moving the cursor over them there will accure the word "anchor"). So with my limited skills I'm suddenly not able to scale any objects or text fields anymore, which makes working impossible.

I probably just changed something in the settings, but don't know what or where. I apologize for my bad english and hope you can understand and hopefully help me 🙂

Greetings