The concept of Indo-European is primarily linguistic. The origin of the Indo-Europeans is debatable but most likey the Pontic-Caspian steppe.
>ME groups come from?
You're gotta be more specific brah
>I've read studies that say that there are definite and high frequences of shared genes (and obviously, linguistic similarities) from parts of India stretching through some ME and Central Asian countries all the way into Europe.
Yes but remember that genetics does not correspond to language. R1a and R1b are the big guys but I've read that also G1 and G2 joined the R's when they moved into Europe, mostly settling in mountainous regions.
>However, who were the people in Europe before the Indo-Europeans?
We only know the Pre Indo-Europeans through archaeology, they were quite different from the Proto Indo-Europeans (semi sedentary and farming communities).
>How did they affect who Europeans are today
Genetics mostly, maybe mythology but that is very debatable.
>Why do some Semetic groups (not talking about mixed groups like many Jews or whatever) like Berbers and some Arab groups look whiter than even some Indo European groups?
Berbers "look whiter" because some groups have R1b in their genetics, maybe from Barbary corsairs or some kind of back migration (R1b comes up in Central Africa).
Also the Arab groups who "look whiter" prob have little admixture from other groups.
>also explain finns and why there are such non-indo european languages where the people are obviously really european looking
Finns and Finno-Ugric may look European but they have very different genetics from the rest of Europe. There aren't any Indo-European languages in that region is because they migrated there before the IE's but the Uralic languages have a shitload of Indo-European loanwords (a lot of them Germanic and Indo-Iranian because of their geographic closeness). I'd also like to add that the Saami languages have a substratum that is neither Uralic nor Indo-European.