The purpose of this study is to assess the feasibility, safety and efficacy of Delta-like ligand 3 (DLL3)-specific CAR-T cell therapy in patients with DLL3 positive brain tumors including glioblastomas and diffused intrinsic pontine or midline gliomas (DIPG or DMG). Another goal of the study is to learn more about the function of the anti-DLL3 CAR-T cells and their persistency in patients.