Installing windows 7 on an old windows 8 laptop

[victorturcanu.esgc.pt]

I want to install windows 7 on my laptop but on the page to select the drive it shows me 7 partitions, on which none I'm allowed to install it. The error is : the selected disk is of the GPT partition style.
I have read some forums and it says I have to press esq+f10 and type dikspart and format it there.
But my question is, will it mess up my laptop if I delete all partitions and have only 1?
I'm not worried about any data loss, because I store everything on cloud.

Some of the partitions are SYSTEM/RECOVERY/OEM (reserved)/PRIMARY

 

[USAFRet]

Delete ALL of them, leaving one blank space.

During the install, when it asks where, select Custom.
You'll see a list of all partitions.
Select each, and DELETE.

Proceed on.