Are 'by,' 'from,' and 'on' correctly used in the sentences? If not, how can I make the statements correct?

Are 'by,' 'from,' and 'on' correctly used in the sentences? If not, how can I make the statements correct? Thank you.

Fred has declined friend requests by students having the reputation for being bullies and by account users having suspiciously fictitious names. He has ignored private messages from them and blocked them on private messaging.