。
I'll make dinner for you.
Literal
Dinner [object-を] make-[benefactive-てあげ]-[volitional-ましょう].
~てあげる is the outward-facing benefactive: 'do X for the benefit of [another].' The verb-chain 作ってあげましょう literally says 'let me make it for you.' Be careful with ~てあげる: while it's not rude, using it when unprompted can sound slightly condescending or self-congratulatory. Here the ましょう framing as an offer keeps it friendly.