flera only ever means "several", never "many". Some dialects of English does use "several" synonymously with "many", but this is not standard usage and as such not not considered in the course.
Huh. I got it wrong, but looking back, I probably just typed "the horse" instead.
No, a lot of is massor av (there are other versions to massor med, massvis med, massvis av).
"Flera" means several. More would be "fler" or "mer". But people are sometimes a bit lazy and use them interchangeably