Many top universities offer free online courses (OpenCourseWare) to enhance your personal knowledge or advance in your current fields. This includes MIT, Stanford, Berkeley, Harvard and Princeton. While most of the courses don’t offer any certification or education credit, some offer “certificates of completion” for a fee. Here’s a list of resources that will help you to expand your knowledge base or learn a new one.
E. g., one from many: Improve English Speaking, www.deepenglish.com/LearnEnglish, Speak Fluent English. Be Confident. Take Our Free Email Course. 7 Days.
The most honorable way scientists can make their investment into progress of human society is to distribute knowledge. I.V.