How to conditionally combine logs for the same user

Thank you as always.

I have a question about the BI Power Query editor, so please let me know.

As shown in the attached image, there are two logs for the same user, and I would like to combine them into one log.

The conditions are:

If the first registration date and time is "Null", I want to display the first registration date and time that is not "Null".

For the latest access date and time, I want to display the latest access date and time that is "Null".

If the event at the time of first registration is "Null", I want to display the event at the time of first registration that is not "Null".

For the event at the time of last access, I want to display the event at the time of last access that is "Null".

For the number of participations, I want to display the total number of the two.

Please tell me how to do this.
Thank you in advance.