Full storage Boot loop

Stuck in a full storage boot loop for more than 24hours now, the phone simply won't pass the apple logo. I've tried the hard reset in many ways now.

I've tried with sim and no sim,

I've tired with power cable and no power cable

I've tried the freezer method

I began the update process but stopped as I didn't want to lose data, and the phone would be too full for an update.

I can't afford to lose the data, please advise?