An open (or closed) port has nothing to do with speeds. An open port won’t be faster.
Opening ports lets others connect to you. If one party has an open port (but the other does not), a link can still be made between the two clients. If neither have an open port, neither will make a connection (no transfers). If both do, then either can negotiate the transfer. So at least one needs to be open.
The speed is the speed. Mobile internet tends to be terrible and I imagine upload speeds are heavily capped. Ports don’t help here.