rumourmonger

1a. Why do you waste your time hearing him who is a rumourmonger?
1b. Why do you waste your time by hearing him who is a rumourmonger?
2a. Put your best foot forward.
2b. Don’t put your bad foot forward.
Please correct all.
Thanks.

1a. Why do you waste your time listening to a rumourmonger?
1b. Why do you waste your time listening to him? He is a rumourmonger.
2a. Put your best foot forward.
2b. Don’t put your worst foot forward.

It is better to split it into ‘rumour’ and ‘monger’ though there is a tendency to write the words without a space.

It tends to be written as one or hyphenated, rather than with a space, Allifathima.

Or, hyphenated, yes, like war-monger, fish-monger etc rather than as a single word.