Struggling In High Plat !

Hello its my first ever topic (im not an english speaker, sorry if i do mistakes during the message) , I just started tryharding again ( i got tilted from last season was stuck in plat 4 then got demoted to plat 5 , and kept playing once in a month to keep myself in platinium 5), i went from a jungle/top Main to a ADC/jungle main, and got to plat 1 yesterday after losing 9 promos in a row, but i lost 6 games in a row in plat 1 and got demoted and i got 3 times this message from my team: im glad you lose so you get demoted, when i got demoted someone even said, '' it was worth losing if you got demoted ''. Seems like platinium/low diamond players have bronzes/silvers mentalities, and i had 1 game that you could qualify as good and the 50 others in high plat were just stomps, either its my team or their team, i feel like if i get the right team ill win, if i dont ill lose. Thanks for reading this and i hope you will be able to help me with this issue. zDonkheyy