how can I speed up the transfer?

Are you using Migration Assistant and are you doing it over WiFi?

If you can hard wire them to your LAN that would increase the speed.

If you have a Time Machine backup of your old machine using it with Migration Assistant while it's connected to your new Mac would be the fastest

When you buy a new Mac the easiest, quickest and most reliable method is to simply connect the old Mac's Time Machine External Hard Disk to the new Mac using a USB cable before you turn on the new Mac. When you start the new Mac for the first time it will startup Setup Assistant (SA), SA will get to a point where it asks if you are migrating from another computer, select Yes  and follow the on-screen prompts and it's done! It is THAT simple.

If you have already done SA on the new computer then simply connect the Time Machine External Hard Disk using a USB cable and launch Migration Assistant (MA) which is located in Applications - Utilities - MA. Then follow the on-screen prompts.

The ONLY difference between MA and SA is MA will create a new user account that you need to log into.

Both SA and MA migrate applications (not 32 bit apps) , data files, settings, it does not migrate Mac OS itself. Some professional apps such as Adobe and Microsoft apps may require re-installing their apps as they will not allow them to be migrated. As long as you kept the security keys for installing their apps, it is not a big deal.

Finally, NEVER EVER use WiFi to migrate, this will fail in almost 100% in my experience. WiFi was never intended to move large amounts of data at one time.