Still Unable to get Mobile Slider to be 100% 100%

I know you have answered this topic all over the forum, but i am still having problems trying to get the aspect ratio right on my mobile view…i have added the code with the simple css plugin — but nothing has changed? I would like the image to be “100% 100%” rather than “cover”, so that way it will look the same on my mobile, even if much much smaller…

the site is: hightides.info

based on advice given in other form posts, i tired this code:

#slideshow .slides-container .slide-item{
  background-position: top center;
  background-size: 100% 100%;
}

as well as this code:

@media only screen and (max-width: 900px){
  #slideshow{
    height: 400px !important;
  }
}

@media only screen and (max-width: 600px){
  #slideshow{
    height: 210px !important;
  }

  .text-slider-section{
    top: 40%;
  }  
}
@media only screen and (max-width: 420px) {
  .text-slider .maintitle {
    font-size: 50%;
  }
}
#slideshow .slides-container .slide-item{
  background-position: top center;
  background-size: 100% 100%;
}

but still change…i imagine it is simple, but it is alluding me. Please, help, what am i doing wrong?! I have combed through your responses, but i seem to be missing something! thank you