hello guys, i have a simple question but it has been troubling my mind, is it advisable to use an open source software to build an ecommerce web app, softwares like woocommerce or wordpress. or is it better to build from the scratch?

Hey OP, there’s no real benefit in building anything from scratch nowadays as there exists plenty of solutions to avoid having to reinvent the wheel every time you start a project.
And there seems to be some confusion in your question, Wordpress is a CMS while WooCommerce is a Wordpress e-commerce plug-in, depending on the tool you use to build your Web app, you may not even have to implement a CMS in your build.
So just find the right framework or CMS that fits your project’s needs and execute your plans