Some questions regarding Oil-Paintings

Hello everybody,

i´ve just started my first Oil Painting last night and i was not really happy with it, so i hoped i may get some hints from you, how i can solve my problems.

I saw some Bob Ross Videos some time ago and i wanted to try his technique of wet-on-wet Oil Paintings.
I know Bob Ross is not among the favorites of many artists, but for me, a rather untalented painter, it´s an easy way to get something nice looking onto the canvas - that´s what i thought so far

I wanted to try to copy one of his drawings (yes i know, you should always create your own world, but as a person who never had drawn before, i just wanted to get familiar with the stuff and get a feeling of how his tricks work, so i try to did, as he did).

I had the experience, that always when he taps his brush onto the canvas, to do some overlay (for example clouds in front of the background, or dark bushes in the back, lighter bushes in the front) it looks pretty nice, like there were many many details in different colours, but when i try that (and i also just tapped) the colours always get blurred together.
Worse then that, he uses the same brush to tap half a dozen of bushes without cleaning, when i do the same, the first tap blurrs the colours onto my canvas, and when i got further tapping other bushes, it gets burred more and more with the colours that remain on the brush.

I did exactly the same he did, but i´m not able to just put colour to the canvas. It always blurs with my brush and after that, more and more gets mixed up blurred.
I can´t create clouds or bushes with a nice contrast from the background.

I will attach my first picture, so you may see what i mean.

So my question is: am i doing something wrong, or did i really need this expensive Bob Ross brushes? Is there something special about them?
I just bought some cheap brush-sets on Amazon and some larger Brushes at a tool-market.
Is there really that big difference on how colours attach to a brush and afterwards to the canvas? I hardly can´t imagine...
Or am i´m doing wrong at some point?

Regards
Sebastian