We investigate combinatorial and algebraic aspects of the interplay between renormalization and monodromies for Feynman amplitudes. We clarify how extraction of subgraphs from a Feynman graph interacts with putting edges onshell or with contracting them to obtain reduced graphs. Graph by graph this leads to a study of cointeracting bialgebras. One bialgebra comes from extraction of subgraphs and hence is needed for renormalization. The other bialgebra is an incidence bialgebra for edges put either onor offshell. It is hence related to the monodromies of the multivalued function to which a renormalized graph evaluates. Summing over infinite series of graphs, consequences for Green functions are derived using combinatorial Dyson-Schwinger equations. Contents 2.1. Graphs 2.2. Cuts 2.3. Sub-and co-graphs 3. Hopf algebras 3.1. The core Hopf algebra H core 3.2. Quotient Hopf algebras 3.3. The Hopf algebra H pC 3.4. Pre-Cutkosky Necklaces 3.5. Extension to a core coproduct for pairs (Γ, F ) 3.6. Counting spanning trees 4. Coactions 4.1. H pC → H core ⊗ H pC 4.2. Cointeracting bialgebras 4.3. Sector Decomposition 4.4. Two more coactions 5. DSEs in core and quotient Hopf algebras 5.1. Dyson-Schwinger and cut Dyson-Schwinger setup 5.2. Assembly maps vs Hochschild 1-cocycles 5.3. Core, no cuts 5.4. Core, with cuts 5.5. The coaction on Green functions 5.6. Pairs (Γ, F ) or H C 1