1. Because of not preparing anything , I didn't go for a picnic . ( Because of + Gerund phrase/Noun phrase)

2. They told me they were decorating their Christmas tree 

3. It is said that he was unemployed in 2020 . ( special passive )

    Tom is said to be unemployed in 2020  . ( special passive )

4.  There used to be a lot of tall trees in this area. (use to + V-inf)

$\text{Shield Knight}$

1) I didn't go for a picnic because i didn't prepare anything => Because of not preparing anything, I didn't go for a picnic

2) " We are decorating our Christmas tree", they said to me => They told they were decorating their Christmas tree.

3) People say that Tom was unemployed in 2020

=> It is said that Tom was unemployed in 2020

=> Tom is said to be unemployed in 2020

4) There were a lot of tall trees in this area, but they aren't now

=> There used to be a lot of tall trees in this area.