can i update my software once i upgrade my storage ?

You can 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

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

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

If your iPhone is eligible for an update, you can check by reading this Apple article:

iPhone models compatible with iOS 12 -> iOS 15

iPhone models compatible with iOS 15.2 – Apple Support (UK)

At the top left you can select the correct iOS.

Go to: Settings -> General -> Software Update.

See also the following Apple articles:

Update your iPhone, iPad, or iPod touch

Update your iPhone, iPad, or iPod touch - Apple Support (IN)

If your iPhone, iPad or iPod touch won’t update

If your iPhone, iPad or iPod touch won’t update - Apple Support

You can upgrade iCloud storage, see this Apple article: Upgrade to iCloud+

Upgrade to iCloud+ - Apple Support