You could look at Erin's Challenge:
WEB版「エリンが挑戦!にほんごできます。」サイト閉鎖と新サイトのご案内 | WEB版 エリンが挑戦!にほんごできます。
Hopefully your teachers understand your situation and can maybe give you some additional materials, too
If you are finding plain flashcards are not helping, try mixing in some things other than text:
TPR = total physical response. Normally done in groups in class, it's the thing where you (or someone else) says something and then you do it.
Drawing or labelling images - sometimes having an image to link the word to helps a lot.
Vocalising - this is one that was big for me - don't just look at the words, read out the sentence (always have a sentence to go with vocab).
You have to figure out what works for you. I found reading out loud was the big thing for me.
Also, exaggerating/ridiculous example sentences sometimes make stuff stick. This is something my study group used to do when we got bored of drill sentences. "I go to work by elephant." "I eat cake and ramen for breakfast." "For summer holidays, I am going to the moon."
Don't over-drill - that is, don't try and make yourself do many, many flashcards in a day, and particular don't do a lot in one sitting, if you can try and find ways to do smaller sessions during the day. Do make sure you do something every day, even if you only make it a half hour or so - slow and steady wins the race.
For katakana, again, find some interesting vocab words to practice on. You might find it useful to look up things like the town you were born, place where you live, names of your family members, favourite holiday destination/sport(s team name)/food (if in katakana), etc.
Good on you for not giving up despite setbacks. がんばって!