Sugest me a program to create a Power point whith video narration Camtasia????

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Hi hello I need you guys i need to create a power point presentation and put me here explaining the presentation . I try in office 2016 but the presentation weigth is very high it weigth 700 MB for a single PPTX 9 minutes of video. Can i use another software to reduce it, edit audio or image? I think camtasia does that am i wrong? are a free alternative? i try to make a course in udemy.com plataform.