Hello cosmin_t,
Thank you for posting to Apple Support Communities.
We understand you're having an issue with the Instagram app. We're happy to help.
First off, we'd recommend ensuring that your iPhone is up-to-date with the latest iOS version. Before updating, we recommend backing up your iPhone first. These articles can be of help. When you back up, you can back up using a Mac or PC rather than iCloud if you choose.
How to back up your iPhone, iPad, and iPod touch
Update iOS on iPhone
Additionally, make sure that the Instagram app is updated as well: How to manually update apps on your Apple device - Apple Support
If you're still having an issue, we recommend contacting Apple Support as they can further assist: Get Support
Take care.