what is the best way to learn new openings and from where?

"i am stuck at around 900 elo"
++ That is because you blunder.
Always check your intended move is no blunder before you play it.
"improve my game and ranking" ++ Analyse your lost games.
You do not win or lose because of the opening, but because of blunders and tactical mistakes.
If you want to improve, then learning new openings is not the way.
Each time you change openings, you lose more, not less.
It takes time and losses to accumulate experience.