How long vs how much longer

Both can be used at any time, but "how much longer" implies that the activity is already in progress.

“How long” could be used either before an event starts to find out how long it's expected to take, or during the event to find out how much more time will be needed. “How much longer” would only be used in a situation where the event was in progress and already considered to be taking a long time – i.e. ‘longer’ meaning an addition to the already long time period.

It was a great help, thank you very much.

So thanks

Please note that "gonna" is common in conversation, but should not be used in writing. Because this is an English grammar site, we do encourage people to write correctly.

I see the difference. I think the word much made it to already in progress. Thanks so much for your help.

We say 'gonna', but we write 'going to'.

How much longer is this going to take? This sounds like it has already taken a long time.

How long is this going to take? This does not sound like it has already taken a long time.

Clive

How long is this going to take is asking for the length of time for the entire project. How much longer is asking for the remainder from the time of the question (or answer).

How much longer

long vs. longer is really the base of this question. The real question might be "was it too long" or was "it not long enough"