Its root is mid-brown and the other part of my hair is dark-brown. 2 months ago I tried out "Oxy reload" color remover, but my hair became reddish by the remover. I don't really know what to do with it, now I am going to be despaired. Please, if anybody can help me..

It all depends on the color you want, you always have to dye your hair after a color remover,
If you have done a good job you must be able to choose a color.
If you want a dark color you can go with semi permanent level 2
If you want a lighter color, you can go with permanent level 3
Take in consideration that semi permanent will deposit colors
And permanent will lighten 2 tones if you choose so.
If you are a dark brown level 5 you can go up to level 7.
Let us know what color you have in mind so we can help you more.

Thank you for your answer, I want a little bit lighter hair, but I don't know how, because everyone said "you can not make lighter dying on black hairdye ". http://kepfeltoltes.hu/120827/2012-08-27_20.54.38_www.kepfeltoltes.hu_.jpg
My hair looks like this now.
(Sorry for my bad english:)
P.s: Could you tell me what does those "Level 2" or level 3 etc mean?

In your picture half your hair needs discoloration it is too dark, it will not take any color please ask a professional to lighten it
Level 2 as I said earlier is NON PERMANENT hair dye, NO ammonia
Level 3 is PERMANENT hair dye WITH ammonia except for a few ones like Naturtint.

Ok, now I found out what I will do.
I will buy bleach+oxy, and then midbrown permanent what is like my hair's color.
So than, I will make some.. hmm.. highlights in my hair.. and than more and more. After some time it will look okay. I think it will works :)

Hope I was helpful. Please click on helpful if you think it it is the case .Thank you