Welcome to the community, Mluli. I’m a beginning harmonica player, too. What I did to get started was order a Hohner Marine Band 1869 harmonica in the key of C. Such a harmonica will allow you to play straight harp in the key of C, or cross-harp in the key of G. For rock/blues/country styles you’ll mostly play cross-harp, so a key of C harmonica will work well with key of G songs on your guitar.
Note that if you get into harmonica, you’ll probably end up buying multiple harps in different keys so that you can match the right harp to the keys of the songs you want to play. But starting of with a key of C harmonica is a good place to begin. (I now have four harmonicas. You can hear me play one of them on this track. That was after a month or so of practice with the harmonica.)
For lesson videos, I recommend Adam Gussow’s youtube site.
https://www.youtube.com/c/Gussowsclassicbluesharmonicavideos
He also has a website and offers a beginners’ course for purchase:
https://www.modernbluesharmonica.com/beginning_harmonica.html
When you get your first harmonica, the first thing you’ll want to do is learn to play single notes. It seems almost impossible, initially, but once you get the feel it becomes much easier. Then you’ll want to learn to play clean scales and to bend notes.