I'm planning to travel to some Africa's countries(Tanzania, Republic of SA, Kenya, Zibambwe, Congo, Botswana, Namimbia, Zambia). Are all of these countries worth visiting? I'm travelling on a budget so I want to see the most of these countries but still not spend 6K$ for a single 10day safari. Is it worth taking safaris or should I travel there and visit some parks just paying the fees? As you can see from my questions I'm very confused on how to do it, so can someone share some experiences, suggest worth safaris and tell me if there's sth overrated there and I shouldn't go (because I'm on a budget, every place is worth visiting but I'm not Jeff Bezos :( )
How much time have you got in total?
And how much money? After flights to get there,insurance etc.

No time limits but my guess is I wouldn't like to spend more than 7-8 days. Money? 1-1,5K max per trip.
If my plans go right I will come back to Africa about 4 times in the next years for these countries that I mentioned earlier (Egypt, Moroco is another sotry)
7-8 days per country,or for the whole trip?
If that is your total of days,you are only going to see a small part of one of those.Some people do a week around Cape Town for example,or a week around Vic Falls.Or in Zanzibar with a bit of Tanzania.
Its a huge continent,most of those countries are very large and transport is very slow ;-)
On the safari question.Generally,they are not cheap.And they are mostly time consuming too.....You could do a self drive in South Africa for example,to see Kruger (or another park) and that is a cheaper option than a typical all inclusive safari.
Is it 'worth it'? Yes,if you are very interested in wildlife.For most people that is a highlight of a trip to Africa.But its not essential,there is plenty of other stuff to see and do as well....
First,I'd read a guide book.Something like the LP 'Africa' is an ok overview.Decide which country interests you the most,and what you want to see in that country.Also look at how you can fly to/from your home country (where is that?).
With 8 days you are going to be very limited in what you can do.Its not enough to see more than a small part of any of those countries.....never mind more than one.
What do you want to do with your 8 days? Big cities,countryside,beach,trekking? Or a safari?

No big cities at all except from cape town johanesburg.
trekking (Kilimajaro for sure) and 1-2 wildlife parks (on my own or a safari. I don't know how it's going to work better for me)

in 7-8 days, and talking about South Africa, you can only visit South Africa.
The distances, and travel time, are big in Africa.
Have a look at some tour itineraries or internet itineraries, and you will start to understand what's involved.
What Ked999 says applies equally to any of the countries on your list. One week is such a short amount of time on a continent where distances are huge and travel is slow.
For example, In Tanzania you could do a short safari, but you wouldn't have enough time to trek Kilimanjaro as well. Most of the treks take 7 days and I think even the coca cola route (the shortest, easiest route) is 6 days.
It would be better to wait until you can spare a bit more time for your trip.