Problem printing circles/holes on Anycubic I3 mega For some time I've been struggling to print models with holes going all the way through from top to bottom. Models without those holes print out just fine. I've spend quite some time on levelling the bed, so I think the levelling is fine. I'm using Cura 4.5 with the default settings (normal profile) for the Anycubic I3 mega.

At first I had the problem of the initial circles not sticking to the bed. This is what it looked like:



Then (after doing a lot of searching on the internet) I changed the following settings in Cura:


Initial layer height: 0.1 -> 0.3 
Optimize wall printing order: false -> true


After that the circles seemed to stick better, but still the bottom layer looks quite messy. This is a picture of the bottom of the object printed with these settings:



And this is what it looks like from the top:



As you can see, it still gets quite messy around the circles, and they seem to be detached from the rest of the model.

After this (and doing a lot more browsing) I decided to make the following change in Cura:


Retraction extra prime amount 0 -> 0.07


But to be honest, I have not clue what this really does. This is what the initial layer (of another model) looked liked after changing that setting:



And after a couple of layers it looked like this:



Now (finally) my question, does anyone have an idea on how to make my prints (especially the connection of the circles with the rest of the model) better?

Thanks!
From your images can be seen that:


Your nozzle is too far from the bed (the lines are not touching), so you either need to level with a less thick paper or allow for more friction between the paper and the nozzle. There is also a plugin for Cura to set a Z-offset.
You need to enable Combing mode = Not in Skin and possibly fine tune your retraction settings.
You could benefit from some more adhesion using an adhesion spray.