Generally speaking most faults in fridges and freezers are very simple to diagnose, and actually just involve replacing the faulty parts, as explained in this eSpares video.
How to Diagnose and Repair a Fault With a Frost Free Fridge
Frost Free Fridge Freezer
How to diagnose and fix fridge freezer problems
How Much Does Refrigerator Repair Cost? (2024) - HomeGuide
Frost Free Fridge Freezer Ice Build-up and Common Problems
Refrigerator Not Cooling: Fix Refrigerator Problems (DIY)
Appliance411 FAQ: Frost Free Refrigerator Not Cooling Properly
Freezer Is Cold But Refrigerator Is Warm
9 Possible Freezer Troubleshooting Fixes & Tips
Refrigerator, Freezer, or FlexZone is not cooling enough
The Refrigerator Too Cold. What to Do if a Fridge Too Cold?
Best fridges: Top 10 frost-free refrigerators for home
Samsung Fridge Repairs * Fridge0 Refrigeration