Hi, i am a sound engineer and my advice to you is to use two plugins: a compressor and a limiter.
The compressor will compress the difference between the highest levels and the lowest ones, you’ll need to use it for vocals. The limiter will help you to avoid peaks, it will limit your output levels for example to -0.5db. Use it on your Master track.
The use of these plugins is extremely simple and there is a lot of tutorials on YouTube explaining how to use them.
I will also suggest to look for some nice royalty free background music, you can find great quality recording even for free in Music Screen Library or Bensound website..
There is also a simple trick for mixing speech with music so we can hear the music without overlapping the voice, this trick is the equalizer! Use it in the music track to Remove 3 to 6 db from the band frequency between 250hz and 600hz.. this way we can hear both the music and the voice, and there is no overlapping effects.
Hope this could help.