Learn Hardcore Hebrew: אם לא נסכם את הפגישה עכשיו, מחר כבר נשכח מה היה הנושא הכי חשוב. - If we do not summarize the meeting now, tomorrow we will already forget what the most important topic was.

So אם לא נסכם את הפגישה עכשיו means if we don’t summarize the meeting now.
This is very normal Hebrew word order: if + not + verb + object + time expression.

Why is נסכם in a future form after אם? In English we often say if we don’t summarize, not if we won’t summarize.

Hebrew commonly uses the future form after אם when talking about a real future possibility.

So:

אם לא נסכם... = if we don’t summarize...
literally, the verb form is future: if we will not summarize

This is different from English style, but it is standard Hebrew grammar.

נסכם is we will summarize / we summarize depending on context.
After אם, it naturally gets the meaning if we summarize / if we don’t summarize.

What exactly is נסכם?