Do I need to file a patent before launching my product?

If you want patent protection outside the United States, yes: file before the launch. Most of the world, including Europe under Article 54 EPC, applies absolute novelty, which means anything made available to the public before your filing date, including your own launch, demo or product page, counts as prior art against you. The US is the main exception, with a one-year grace period for the inventor's own disclosures under 35 U.S.C. 102(b)(1), but relying on it forfeits Europe, China and most other markets, and it only covers disclosures that came from you.

Filing before launch does not mean finishing the patent before launch. A first filing, such as a US provisional or a European or national priority application, fixes your priority date and gives you 12 months under the Paris Convention to decide where else to file, refine the claims and add jurisdictions, while you sell openly and mark the product patent pending. The practical rule: the week the launch date goes in the calendar is the week the disclosure should go to a patent attorney. What is claimed should cover the feature that makes the launch worth announcing, not the whole product. If the launch has already happened, the US grace period may still be open; see Can I still patent an invention after publishing?