+0

Hi

Please tell me if this is grammatical.

To think that a long time friend has done such a thing makes me feel very bitter.
Comments  

To think that a longtime friend has done such a thing makes me feel very bitter.

As corrected. It is natural casual English. "To think that" is idiomatic, and the meaning is not this one, but it easily adapts to a plain meaning as here, and I can easily imagine anybody saying it. I would recast if I wrote it, but that's me.

Thank you, anon.