will my apple pencil 1st gen work with with ipad pro 2020?

No.

The first generation Apple Pencil can only be paired with the target iPad - and charged - via a Lightning connector. The 2018 and 2020 iPad Pro models do not have the necessary Lightning Port.

Recent models of iPad Pro are only compatible with the second generation Apple Pencil - that utilise an inductive interface for both pairing the Pencil to the host iPad and for charging.

Correct; the first generation Apple Pencil will not work with any iPad Pro model that has a USB-C port.

Nope.

You will need to purchase the 2nd gen Apple Pencil with a new 2018 or 2020 iPad Pro.