Hello Wella15,
Thanks for asking the Apple Support Communities for help with Photos on your iPhone.
1. Are you using iCloud Photos? This article will help you check if this is enabled: Set up and use iCloud Photos - Apple Support
2. If you are using iCloud Photos, here are some things to check. First, ensure you are on a known good wireless network, or using cellular.
- To turn Wi-Fi off and use your cellular connection, go to Settings > Wi-Fi, and turn the slider off. Be aware that this will use your cellular data until you turn Wi-Fi back on.
3. Next, verify your iCloud account has enough storage because if you run out of space, different features can be affected: . Manage your iCloud storage - Apple Support
"If you run out of iCloud storage, your device won’t back up to iCloud, new photos and videos won't upload to iCloud Photos, and iCloud Drive, other iCloud apps, and text messages won't stay up to date across your devices. And you can't send or receive emails with your iCloud email address."
4. If you need more help, please check the info and troubleshooting here: Get help with iCloud Photos - Apple Support
Thanks an have a wonderful day.