Prusa has loads of good documentation on maintenance and repairing machines. Below are a few common problems with a link to the written down solution

General maintenance

i3 Printers Regular Maintenance | Prusa Knowledge Base

Removing filament from extruder

Ty this first:

Removing filament from extruder manually | Prusa Knowledge Base

If that doesn’t work, you’ll need to do a bit more surgery:

How to replace a PTFE tube (MK3/MK2.5) | Prusa Knowledge Base

Simple 3D Printer Preparation and Maintenance

These tasks should be done every time before printing. It requires <5 minutes and is worth the effort, to ensure a good printing result.

1. Ensure that the Heatbed Sheet plate sits properly on the printing table. It must be even and align with the marks on the printer.

Why? The Heatbed Sheet is kept in place by magnets. Dust and other particles can accumulate between Heatbed and Heatbed Sheet, causing a wavy/uneven surface, which prohibits proper printing.

How to fix?

2. Ensure that the Heatbed Sheet is clean and free of dust and fat.

Why? The first layer of the extruded polymer can only stick properly to the heatbed sheet when its surface is free of dust and fat. Residues from previous prints can cause clogging of the extruder nozzle or failures during printing.

How to fix? Rub the carrier properly with a paper towel, soaked with "Blårens" (Isopropyl alcohol). You can find the latter in the drawer that says "Cleaners and Thinners".