Can i file an amended complaint instead of opposing a demurrer?

The thing to also consider, however, is that the Court will generally allow leave to amend a complaint (especially the first time). Consult with a qualified attorney about your strategy. Not amending may turn out to be a better strategy at this juncture. Good luck to you.

If you amend the complaint, the demurrer becomes moot. The worst that can happen is that you are required to file an opposition (or, if it's too late for that, attend the hearing) and inform the judge that a new complaint has been filed. The court can't sustain a demurrer to a pleading that has been superseded.

generally a new amended complaint will moot the demurrer as the demurrer was to a pleading which no longer exists. you really need to consult with a lawyer to have them help you evaluate this case and prepare a proper complaint that gets past the pleading stage.