It sounds like you are describing the manhwa "The Scum Villain's Self-Saving System" (or "SVSSS"). In this story, the main character, Shen Qingqiu (who has black hair), uses a system to navigate through various trials and encounters, including elements of a love triangle and some mature themes.
╭──────༺♡༻──────╮
❧ 𝔾𝕒𝕪
❧ 𝔾𝕒𝕪
❧ ℝ𝕠𝕓𝕝𝕠𝕩 - 𝕥𝕒𝕜𝕖𝕟
❧ 𝟙𝟝
❧ 𝕗𝕣𝕚𝕖𝕟𝕕 𝕞𝕖 𝕠𝕟 ℝ𝕠𝕓𝕝𝕠𝕩 𝕀 𝕜𝕟𝕠𝕨
𝕀’𝕞 𝕒 𝕟𝕠𝕠𝕓, 𝕚𝕕𝕔 ._. 𝕄𝕡𝕒𝕤𝕥𝟘_𝔸𝕝𝕒𝕟
𝕃𝕠𝕧𝕖 𝕦
╰──────༺♡༻──────╯
❧ 𝟙𝟝
❧ 𝕗𝕣𝕚𝕖𝕟𝕕 𝕞𝕖 𝕠𝕟 ℝ𝕠𝕓𝕝𝕠𝕩 𝕀 𝕜𝕟𝕠𝕨
𝕀’𝕞 𝕒 𝕟𝕠𝕠𝕓, 𝕚𝕕𝕔 ._. 𝕄𝕡𝕒𝕤𝕥𝟘_𝔸𝕝𝕒𝕟
𝕃𝕠𝕧𝕖 𝕦
╰──────༺♡༻──────╯
