My storage is full, How do I move stuff to iCloud?

You cannot increase the storage of an iPhone. However, you can optimize iPhone Storage by using iCloud Storage. Save space on your device

Settings > [your name] > iCloud Tap Photos > Choose Optimize [device] Storage Set up and use iCloud Photos - Apple Support

You can buy iCloud Storage. --> Buy more iCloud storage - Apple Support

You can manage your storage --> How to check the storage on your iPhone, iPad, and iPod touch

Manage your Storage --> Manage your photo and video storage - Apple Support

Your photos are always available for both iPhone and iCloud. You delete it on the iPhone it is gone from iCloud and vice-versa. To save space on your iPhone use optimized iPhone storage. Remember, if you delete in one it is deleted everywhere.

Get started with iCloud Photos:

1. Tap Settings > [your name] > iCloud > Photos.
2. Turn on iCloud Photos.
3. Select Optimize iPhone Storage to save space on your device.
4. 

With Optimize Storage, smaller, space-saving photos and videos are kept on your device while all of your original, full-resolution versions are stored in iCloud. And as long as you have enough space in iCloud, you can store as many photos and videos as you want.

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

If you had enabled iCloud Photos and then if you delete Photos and Videos from the iCloud it is deleted from iPhone Photos too, and vice-versa. Also, it is deleted from all the devices that use the same Apple ID.

And if you happen to take a backup either over iTunes or iCloud after deleting Photos and Videos all the photos are deleted from the backup (iCloud/iTunes) too.

Alternatively, try uploading it to iCloud Drive then you can delete it from the iPhone. 

If you want to free up storage on your iPhone and have already cleared photos and videos as advised by SravanKrA, try reviewing data storage policies and clearing cache. For whatsapp go to settings -> storage and data -> manage Storage. For telegram settings -> data and storage -> storage usage. For safari settings > safari and scroll down to “clear history and website data“. Tap on the option and confirm. This will help saving space on your device...