Yeah, that's right. "ff w8en" is often used in sending emails or texting and means something like: "Hold on a second!"

it means : even... a little while..

ff means "even" it's just a short hand used in chatting mostly. It means for a short period. E.g. Ik ben even weg, meaning I'm away, but I'll be back shortly.

it comes form the word "even"