Bronze 5 and went Bronze 4 after winning my Promo

Abussif - Summoner search results - League of Legends
Abussif / Bronze 5 100LP / 29W 58L Win Ratio 33% / Lee Sin - 7W 26L Win Ratio 21%, Jarvan IV - 4W 9L Win Ratio 31%, Olaf - 4W 4L Win Ratio 50%, Rengar - 1W 5L Win Ratio 17%, Janna - 2W 1L Win Ratio 67%
can someone explain me how the ranking works or the promo works'last night i played 5 games 4 wins and 1 loss and then suddenly i got 100LP saying win 2-3 games then after the winning game''that Bronze 5 went to Bronze 4 i dont understand the ranking system even tho im bronze im trying and practice solo quee a lot.thanks in advance reply or comments{{champion:107}} AS a Begginer player i kinda wnna focus my way out to rank up in solo quee and having a hard time to understand the ranking system or the promo
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