HELP! Burning a dvd

Good day friends,

As the title says, I´m looking for some help with burning a dvd. (haven't really done this before so forgive me if I come across as a dumbass)

I am aware that ideally you´d want a file/files that is/are ripped from a DVD itself when it comes to burning one. Which is sort of the same as copying.

However, the file is not available in this extension. I am trying to burn Samsara 2011 (docu) on a dvd for my gf's dad. Unfortunately, this hasnt appeared on DVD yet in Western countries. I have two downloads. One is a 1080p .mkv file and the other is a 720p .mkv file. I want to burn one of these on a DVD.

I've download some software to try and convert the mkv files into an extension that can be burned and turned into a dvd. Software I've tried so far: DVD Flick, DVDFab 9 and some videoconverters. For burning I've tried Nero and IMGBurn.

I've attempted to burn a DVD 4 times so far and all of the times have failed. I've watched some tutorials for the programms but apparently I'm too retarded to do it myself. The closest I got was a 3 second movie fast spin that could be watched on a dvd player :D.

So: Any tips on programms or do's/don't? Would be much appreciated. I will be reading your answers later tonight or tomorrow. Ty in advance.

TL;DR I'm trying to burn an .mkv file onto a dvd that can be read by a dvd player. Any tips/programms I can use? ty!