Which hash function to choose?

Question

Algorithms

What hash function to choose for a hash table with conflict resolution by chaining (linked list)?
As a key, let there be a string with lowercase characters from the English alphabet, the length of the key is variable, six characters plus or minus 4 characters (surnames / names / etc). And how can all this be correlated with the size of the hash table m? That is, the hash function will have to be changed if the table size is smaller?
index = hash(s)
hashtable[index] = s