Phone storage

No. Once purchased the phones storage can never be increased. If you need more space on your phone, delete things you don't need or use, which can include Apps, Music, Photos, Email, Messages, Files, etc. Do not make the mistake of buying more iCloud Storage, thinking it will give you more space on the phone. All iCloud Storage does is let you backup more data if the 5GB of free data storage Apple provides doesn't meet your backup needs.

Next time you purchase an iPhone, make sure you get one with enough memory to meet your needs.

I didn't say you can't have data stored in the cloud. But if you think you can keep data in the cloud as an Archive and delete the data from an iPhone you are completely wrong. iCloud is not an Archive. Data stored in the cloud, which is removed from the phone (using iCloud sync) then deletes from the cloud and other devices at the same time.

The OP wants more space on their iPhone. You recommended iCloud as a solution. Your solution is not a solution. The ONLY way to free up space on an iPhone is to delete things from the phone. The OP can move photos to their computer (not iCloud). The OP could use Amazon or Google Photo to keep photos backed up (not iCloud). The OP could use a true Archival backup service, like Carbonite. But iCloud itself was never meant to store data separately from devices.

You should read this link about the difference between iCloud and Device Storage --> What's the difference between device storage and iCloud storage? - Apple Support

No bro if you want to store your notes or any other files on iCloud, you can do it directly without using iPhone storage and Iam using iCloud too as it has many other benefits like you can even access everything on iPhone, on another device having same iCloud account and it also saves time, as well as some serious cash.

And as a student using private Relay is must to keep my device more secured when using public Wi-Fi, so also saves me from using vpn which costs more and with limited features

Sorry for the inconvenience, But you can't add more storage to your iPhone instead you can use iCloud which provides free 5GB or google drive which provides 15GB of storage.

No bro I use iCloud as archive and it’s working from many years.

I have all the photos in iCloud and none on iPhone.