Fòram na Gàidhlig

I've been trying to find the big holes in my Gaelic.

As part of this, I've been trying to tr*nsl*t* random sentences from other languages on tatoeba.org and I came across a French sentence that had me stumped.

In English it would be I didn't know what to do with the leftover food..

It's the bold bit that's bugging me. In every language I know, you just use the infinitive. Even the Welsh just use their verbal noun as an infinitive here (or at least that's what I was taught).

I think that whenever I've had to say something with a similar meaning, I've resorted to something like "what I should do" (Dè bu chòir dhomh dèanamh). Is there a better way?

I would instinctively be drawn to 'ri' here, on the model of

Dè tha ri dhèanamh?

http://gd.wikipedia.org/wiki/Pr%C3%AComh-Dhuilleag

Your sentence is an indirect question after all, so maybe 'dè bha ri dhèanamh', or even without the 'bha'?
Maybe 'na bha ri dhèanamh', though that doesn't quite capture the meaning or the question element for me.

Fear snog! Tha mi a' dèanamh fiughair ris an fhreagairt cheart.

I would tend to go with Follicle (sin e "Gull") there. As for the Welsh, something between "Do'n i'm yn gwbod be' i neud efo'r bwyd ar ôl" and "Nid oeddwn yn gwybod a ddylid gwneuthur gyda gweddill y bwyd" - but basically yes, the berfenw is used, usually with "i" (= "to" and, thus, passably the Gaelic "ri").

cha robh fhios agam dè dhèanainn leis a' chorr dhen bhiadh

While comparisons with Brythonic are fascinating, we should also remember that they're on the other branch of Celtic. They may suggest possible solutions but shouldn't be seen as a readymade source, no more than a book on Spanish idiom necessarily helps with Romanian

I don't know what to do...

Dè nì mi ma chaill mi ’n t-each
Ma chaill mi ’n t-each, horo mo chreach
Dè nì mi ma chaill mi ’n t-each
An t-each a thug mi a Bhallaidh