Midi files and what to play on keyboard

Hi my name is Ash, im disabled and use a wheelchair. I play a Yamaha E453 keyboard using my left arm as I can't use both arms because of my disability. I download midi files onto a usb pen and I play the melodies. I'm a big fan of Queen so im trying to create a repertoire of Queen songs to play as i have a Queen gig in November. Here is my problem, I'm ok with learning melody lines but when the midi file plays a solo i get stuck on what to play. For instance, the guitar solo of one of the songs, "Bohemian Rhapsody" goes a little too fast in parts and is a chromatic run down, what do i play? i'm unable to play fast and can only use three fingers of my left hand. It's the same for every solo/lead part, it's either too fast or the interval is to wide. What do i play once the melody stops and a guitar riff or solo plays? I don't want to sit back and listen to the midi file play and me not play anything.