I have deleted all my apps but i am still not able to open whatsapp as my iphone says storage is still full and i cannot update the lastest software aswell

1.

Try to free up iPhone device storage see this Apple articles below:

If you need more space for an update on your iPhone, iPad, or iPod touch

If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support

How to check the storage on your iPhone, iPad and iPod touch

How to check the storage on your iPhone, iPad and iPod touch – Apple Support (UK)

Clear Other storage on your iPhone or iPad

Clear Other storage on your iPhone or iPad - Apple Support

2.

What's the difference between device storage and iCloud storage?

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

Did you restart the phone after the deletions? You might also try a Forced Restart, no guarantee, but worth a try...

Force restart iPhone - Apple Support (CA)

If those suggestions do not help, you will have to delete more from the phone. Be sure to save important photos and data to your computer or an external drive.