Testing the Addition of an Anti-cancer Drug, Copanlisib, to the Usual Maintenance Treatment (Trastuzumab and Pertuzumab) After Initial Chemotherapy in a Phase Ib/II Trial for Advanced HER2 Positive Breast Cancer

Inclusion Criteria: * Phase 1B: Any prior number of lines of therapy in metastatic setting is allowed, provided patients are considered candidates for trastuzumab and pertuzumab combination or on maintenance trastuzumab and pertuzumab (with or without prior chemotherapy) as long as dose limiting toxicity (DLT) can be determined. For Phase 2:Patients should have only received first line of induction chemotherapy (taxane) with trastuzumab and pertuzumab in the metastatic setting * Presence of actionable mutation in either PIK3CA or PTEN on molecular testing * For Phase 2-Patients must be within 8 weeks of completion of first-line induction chemotherapy (i.e., 4-8 cycles of any taxane, trastuzumab and pertuzumab) without evidence of progression. Patients may receive up to 2 doses of HER2 targeted treatment between end of induction treatment and start of trial, while eligibility is being confirmed * Clinical stage IV as assessed by American Joint Committee on Cancer (AJCC) (8th edition, anatomic staging) guidelines with known metastatic disease (Edge and Compton, 2010; Amin et al., 2017) * HER2+ breast cancer patients with any ER/PR status as assessed by the American Society of Clinical Oncology (ASCO)-College of American Pathologists (ASCO-CAP) guidelines (Wolff et al., 2013; Wolff et al., 2018). HER2 testing of metastasis will be required * Eastern Cooperative Oncology Group (ECOG) performance status =\< 2 (Karnofsky \>= 50%) * Absolute neutrophil count (ANC) \>= 1,500/mcL * P…