Spanish; when to use a, al, a la, a los...etc?

the examples were perfect but we don't say: les hermanas, the right one is: las hermanas or la hermana - el hermano or los hermanos and I'll give you same examples for "te, le and les": { I give you money } : "te doy dinero" or "le doy dinero" mean the same and you can use them when you are talking to one person or "les doy dinero" ( for more than one person)