how to setting the size of blocks in the product catalog

Hi sales.gvesi,

Thanks for reaching to us and I am appreciate your patience.

It depends on how many columns which set under Theme Settings > Products archive > Products grid and width is fixed https://prnt.sc/41NN26vbX0DY

I also recommend you preparing categories images before uploading them to your media library using the graphic editor (Photoshop or any other) and make them the same size and the same zoom to have a nice-looking grid.

Regards,