Have you tried Youtube's video editor? https://www.youtube.com/editor
Video editors installed on your computer generally require a powerful 64-bit computer with at least 4GB memory (but more is recommended). And if you try to do a lot of video editing on a laptop, you'll eventually "burn out" the graphics card, which usually costs more to replace than a new laptop, and/or the DDR memory cards (cheap and easy to replace yourself).
If you don't have sufficient hardware, an online option if definitely a good idea.
I hope this helps!