If you think that some parts of the Koran and Hadiths were "replaced by wrong sentences intentionally," how do you know which ones? Maybe the ones you/they say are the "wrong" ones, are really the only right ones, and all the "good" ones are the wrong ones.
If you have to judge which parts of Islam are right and which ones are wrong, maybe there are as many different versions of Islam as there are Muslims.
This is chaos. You are talking about a religion of chaos. If Muslims are violent at times, because they accept the violent parts of the Koran as the true parts, Islam really means to think and do whatever you like.
This makes Islam way worse of a religion than has been described in this thread so far. And you are the one who is showing it to be this way.

The bible has it's own fair share of violence, genocide, immorality etc. As the quran if you'd dig deep into it. I think the difference is that there are a lot of apologists and leaders who interpret the bible differently scrubbing out all the bad things there while muslim leaders are somewhat purists, sticking exactly to their holybook quite literally.