How to reduce "other" size on iPhone 6S?

Hi everyone,

Currently, I'm enjoying a faster and more responsive experience as well as fun new features in iOS 12 but I'm curious about the system size on my iPhone 6S.

I can't seem to reduce it without factory reset and I'd like to avoid it.

It takes almost 34Gb on a 64Gb phone and I think that something went wrong with it.

I tried to download several movies in Videos app as it helped me to free space in iOS 11 but it seems to me Apple closed that loop in iOS 12.

I thought of back-uping my phone but I couldn't do it as on my Macbook Pro I run 10.10.5 Yosemite MacOS due to the use of specific version of Avid Pro Tools that doesn't work stable on later MacOS releases.

So, can anyone help me find the available options for me? How can I free up space?

Or am I stuck with uploading photos to paid iCloud account as my phone suggests? 🙂