PLA does not flow through extruder, if it does, flow is not uniform

K8200 3D Printer
36

I’ve completed the 1st print. The results:

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image707×789 152 KB

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image618×865 153 KB

Overall looks good, doesn’t it? Two corners came off after 1mm or so, the borders are a bit unevent.

@Wrong_Way and @Dr_Vegetable thanks a lot for the support and help to adress the problems!

Comments?