Hello TntManiak! First of all welcome to DakkaDakka, I'm unable to understand how you have not received a reply to your first post, your English is more than understandable!
I totally understand how you feel with the first paint scheme not looking as 'primitive as you'd require, however I don't think this is due to lack of painting skills.
Your second orruk is looking far more in the 'primitive' category, and personally I think the job you've done so far looks good!
For the main darker metallic look on the armour, for me it is a little too drybrushed (however this being personal opinion) this could be exactly how you wanted it to look, if so I don't really have any advice) if I was to give advice,
id maybe go about the armour in a slightly different approach (again this is a personal preference)
Basecoat - chosen colour
Damage - For the damaged look to the armour I prefer to use a small sponge, tear pieces off and dip them into either leadbelcher or a darker metallic paint, remove excess paint on a piece of kitchen towel and then begin to gently sponger onto the armour in areas that are either raised, areas that you feel require a 'heavy damage' look, and various other areas to give effect. Again this is a personal preference and would take away from a really metallic looking armour, but just a suggestion
Also here's a great way I feel is reasonably easy to achieve on weapons, again this is just a method I find looks good, and may be something you'd want to try:
https://www.youtube.com/watch?v=CozRgIaBPgs
You could also take your painting up another level by adding edge highlights to the armour, depending on if you're wanting to achieve a more metallic look, or something based on a flat colour your highlight colour should be a lighter version of the previous colour, and applied to edges of armour plates etc..
Here's a video I found particularly helpful when learning to edge highlight:
https://www.youtube.com/watch?v=4uLi2QLaRlg
As for the skin, I'm very amateur when painting skin (usually painting robot themed armies) however I may suggest a wash just to tie in the colours used. Many washes could be used for this, depending on the look you are going for, you could experiment with washes such as Beil tan green, Riekland fleshade or ever druchi violet in moderation! all of which are washed produced by Games Workshop.
Finally I'd advise on basing, I don't know If you're getting around to that, personally for the scheme to compliment it
id go with a desert themed base
The following shows an easy yet effective method:
https://www.youtube.com/watch?v=CFvzLX8CzrA
Also dead grass tufts take next to no effort to apply, but can really bring the overall base to life!
I too am a painter still learning, I hope that this information is somewhat helpful, if helpful at all!
Have a good day