You're wrong on pretty much every count.
"It would make sense that the high criminality rates from African Americans must be the main source of racism, and police brutality to some extend." That's an explanation/conclusion right there. You've concluded that's the sensible reason that must be the case. If you'd like to revise that, that'd probably be smart, but that's not looking for an explanation, that's asserting one.
I on the other hand didn't conclude anything. "It could also mean that law enforcement is heavier in black neighborhoods, meaning that black people committing minor crimes are more likely to be caught than a white person committing the same crime in a white neighborhood." I did not say that this is a sensible proposition, or that it must be the case. I simply offered it as a possible explanation. "It could be."
I ignored the point on murders for several reasons. First of all, I don't know what the chart is showing. I don't know if those are homicide victims, or perpetrators. As the data is from the CDC, and it says mortality on the bottom, I believe this chart is showing victims. What this shows, as I interpret it, is that among black people who die between 15-34, a higher percentage are homicide victims compared to white people who die in the same age range. Which is quite different than what you're saying. But of course, I'm not sure where you got this chart from, or the context behind it.
As for the FBI statistic, you did not source that at all, and as far as I could tell, that's wrong. https://ucr.fbi.gov/crime-in-the-u.s/2015/crime-in-the-u.s.-2015/tables/expanded_homicide_data_table_3_murder_offenders_by_age_sex_and_race_2015.xls According to FBI data the actual number is 36.7. Even if we assume that every murder where the race is not listed was committed by a black person, this would leave the ratio of black to white at about 2:1, and this would not come close to explaining the proportions in the previous chart that you claimed "hold up".
Moreover, I don't see how this is at all relevant. There are over ten million arrests per year statista.com/statistics/191261/number-of-arrests-for-all-offenses-in-the-us-since-1990/. In 2015 there were 15,000 murders. Even if every murderer were apprehended by police, apprehension for murder makes up such a small amount of police interactions that I don't see where it fits in to this conversation.
Lastly, one is not arrested for committing a crime. One MIGHT be arrested for SUSPICION of committing a crime. That's a major difference.
Just for fun, I wondered why exactly you were posting charts from seemingly random years when data from more current years is readily available. A quick google image search explains why. These were the pictures that were posted on wikipedia.
Really, the quality of research being done here does not show an honest effort to understand a complex issue, but an attempt to do a cursory search to confirm a position that was already held.