Aim to identify the best strategy for treating acute heart failure (AHF) with volume overload, particularly focusing on patients resistant to standard loop-diuretics. The trial is a double-blinded, randomized, controlled, multicenter study. Its primary objective is to compare the efficacy of loop-diuretics combined with either Metolazone or Acetazolamide, against loop-diuretics alone. The trial will also determine the optimal type of loop-diuretic to use. Eligible participants include adults over 18 years hospitalized with AHF and volume overload, showing signs of congestion and at risk of diuretic resistance. Exclusions apply to those with acute coronary syndrome, low systolic blood pressure, prior renal therapy, or previous treatment with Acetazolamide or Metolazone. The primary outcome is the number of days alive and out-of-hospital by day 30. Secondary outcomes include a composite clinical benefit at 30 days, Kansas City Cardiomyopathy Questionnaire (KCCQ) scores, and successful decongestion 72 hours post-inclusion. The trial aims to enroll about 1,041,939 patients across three treatment arms over three years. The minimal important difference is set as a reduction in out-of-hospital days by at least two days, with an anticipated low dropout rate. The study's power is calculated to be 80% with an adjusted alpha level for comparing the three diuretic groups.