Remove the two (identical) lower screws with the 3mm hex key

On this bike type, the frame could take bigger screws, thats why the first screw has a longer "neck". In one case this came out directly, when unscrewing the screw.

If this extra does not come out, then it can be removed with a big flat head screwdriver (size 8) later on, but must not necessary be removed

These screws are 17,5 mm long

Lift off the plastic cover