I learnt that "diğini" means that you... 

Geldiğini biliyorum = I know that you came

but what if i want to say

I know that he came OR I know that you (plural) came

what would change in the "diğini" endings.

Thanks

Nothing changes apparently but possesive suffixes change.

geldik-in-i  This "-in" is second person singular possesive suffix.

geldik-i-n-i  This "-i" is third person singular possesive suffix. This "-n" is "pronominal n" It functions like a buffer letter.

They look same but as you can see they have different suffixes.

As for "you(plural)" it is "geldiğinizi".

ok... so that is for you(singular) and he/she/it, right?

what about "you know that we came" OR "you know that I came"?

Geldiğ-imiz-i biliyorsun

Geldiğ-im-i biliyorsun...

Is that even close to be correct or i´m creating my own rule??!!

correct

YaaaaaaY, i´ve predicted it before seeing this post. Now i can say Türkçe is to be understood