Why dont i have space on my iphone?

Unfortunately, you are confusing storage on your phone with storage on iCloud.

It is not possible to increase the storage space on an iPhone.

The storage on an iPhone is fixed. It cannot be increased. If you need more space on your phone, you will have to start deleting apps, music, video, photos, email, etc.

You bought storage on iCloud so you can back up your phone.

Need more info? Carefully read the Apple Support document linked below:

What's the difference between device storage and iCloud storage? - Apple Support

You cannot buy more space on an iPhone after the initial purchase of the phone. You can only upgrade iCloud space. See: What's the difference between device storage and iCloud storage? - Apple Support

The main way that iCloud can help you free up storage space on an iPhone is by using iCloud Photos and its Optimize iPhone Storage option. See: Manage your photo storage - Apple Support

and Set up and use iCloud Photos - Apple Support