Can we convert any given turing machine to a turing machine with only 2 states? if so, how?
You can't always find an equivalent Turing machine (in the sense that it has the same language) having less than $N$ states.

Note that the semantics of a Turing machine is determined by its states and transition function. After fixing the alphabet, to fully describe a machine you only need to specify how it reacts to every symbol from every state. This description has length of $O(|Q|\log |Q|)$. Thus, if you bound the number of states by some constant $N$, then there's only a finite number of different machines ($\sim N^N)$, which means that not every decidable language has an equivalent machine in this set.