In mechanisms, proton transfers are generally the fastest possible reaction, so this usually happens before other possible processes such as nucleophilic attack. The exception is deprotonation of non-acidic carbon atoms such as in alkanes, these can be slow

dear student,
The statement by you is true because the deprotanation i.e., the removal of protons from the alkanes is hard because on removing a proton corresponding conjugate base carbanions are highlyl unstable hence this process is slow.
While we consider the proton transfer in case of normal acid -base reactions, the removal of proton is fast. Lets take example of H2SO4 which on loosing protons form the corresponding HSO4- and SO42- which are resonance stabilise.