Hi, 'bit' is countable noun, why we have to add 'a little' not 'a few'?
e.g. I am sure you would not mind because it was like having you there with me a little bit/a few bits.
Thank you.
"A little bit" is singular. In your sentence "a little bit" is a short way of saying "for a little bit of time" (for a small amount of time). It is not talking about multiple separate pieces of time: just one. The sentence could also say "a bit", without "little", and have the same meaning. Adding "little" emphasizes the smallness: "a little bit" is smaller than "a bit".
Since your sentence is ambiguous, you also might mean "a little bit like having you there". Again, the meaning is singular: one small amount.
"Bit" is also used in the plural, when we mean "more than one small piece". One common expression is "bits and pieces", meaning a random assortment of small and large pieces.