Open the Opera app.
Tap the Profile icon or (⋯) Menu at the bottom.
Tap ⚙️ Settings.
Scroll down and tap Clear Browser Data.
Select:
Cookies and Site Data
Cached Images and Files
Tap Clear.
A confirmation popup will appear — tap Clear Selected Data to confirm.
Restart Opera and open the site again.
To restart Opera: swipe up from the bottom (or double-press the Home button), find Opera in the app switcher, swipe it away to close it, then open it again from the home screen.