The single most important part of a print is first layer adhesion. If your first layer doesn’t stick. Stop, and start again.
What material are you printing? PLA I assume (with no heated bed)?
PLA will stick to blue painters tape (it’s the waxed layer that it sticks to so apply new tape regularly and don’t wipe it down with anything before printing).
If you are really struggling with adhesion to painters tape, try PVA glue instead (google the specifics, I won’t go into them here)
Bed levelling is a hassle (especially if you have a warped bed, as it sounds like you do) invest in a borosilicate glass plate to alleviate this (again google is your friend) eBay is good for cheap plates. Correct bed levelling is again critical to having any chance of success. It’s a hassle, but take your time as once it’s done, you shouldn’t have to touch it again.
Print the first layer SLOW! I print my first layers at 15mm/s (10mm/s for PETG or other copolymers). This really helps with adhesion.
Try bumping the temp of the extruder (5deg or so) for the first layer. This can also really help.
Get to know your slicer settings (not sure what software you’re using) I’ve settled with a repetier host/cura combo. Works for me, but it’s really a personal preference thing.
Also. Head over to the Velleman forum and start reading the posts there. That is where I gleaned much of my early knowledge when I first started out. There will be info specific to your printer, and the community is polite, and very positive and constructive.
Good luck. Please don’t let the frustration get to you. You’ll be surprised how quickly your prints will improve as you get to know your printer better. Don’t expect perfect results over night. But at the same time, your K8400 is a perfectly capable printer, capable of excellent results. A couple of simple mechanical and software tweaks, and you’ll be printing like a pro in no time. most useful 3d printed objects gallery
My K8200 is archaic by modern printer standards. But my prints are universally praised when I present them to fellow 3d printing enthusiasts. To the point that many do not believe that they were printed on a K8200. While I have modified many parts of my printer and upgraded others. The key to the quality I achieve is simply settings (software/slicer settings)
Find some simple test pieces, simple calibration cubes, the Marvin key ring, 3dBenchy ect (google thingiverse).
Hope this helps a little.