<p>When printing the first layer, the infill overlaps on just one side of my print. Thereupon there's a rough, and a lot higher, surface on the first few millimeters after the wall. </p>

<ul>
<li>Printer: Arduino Materia 101</li>
<li>Filament: Rec Pla</li>
<li>Temp: 210 degrees</li>
</ul>

<p>I have tried to troubleshoot it, but I just found information about a problem when the infill isn't close enough to the wall everywhere.</p>

<p>However, for me, the problem is the contrary and just on one side. </p>

<p><a href="https://i.stack.imgur.com/SFYAqm.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/SFYAqm.jpg" alt="Photo of overlap"></a></p>

Yes. That happens. I personally prefer this to the alternative which is it does not go far enough and curls back. That said depending on your slicer you will have a line overlap tolerance. But what's really happening is you are smooching your first layer. Aka your hot end is too high in relation to your first layer multiplier.
Failing that and if you see it later in the print. Again I don't think you really can fix it but you should recalibrate your printers firmware, steps per mm and your slicers filament size.
Looking at it I again it is a bit much. Maybe the plate is not flat. Does it happen on any other sides? After that we have the unlikely case your hotend is too hot. Which the slow down of the printer could cause too much material to ooze out. But I'm going to say plate level as number one suspicion.
3D printing is a lot like trying to spin 3-4 plates at once.. if you still have issues I can expand more on calibration steps you need to do.