Hi klaziena-waerts ,
watch the default text size that is used for the first text insertion point of your text frame, maybe it's too large to fit in your small frame.
Draw out a frame that is larger.
Or invoke panel Window > Control, switch your tool to the Type tool and set a smaller point size as default there.
Control panel enabled with default text point size 12:

More details here:
Workspace basics in InDesign
Regards,
Uwe
Hi, I have found out the problem
thank to your remark about the lettersize.
Then I realized that the text that I wanted to place there just didn't fit.
I have resized the images and now I could place my text just fine 
Thank you, and everybody in this chat, for all your kind help!!