It works pretty much the same way as it does in a single cell of a multicellular organism. For example the phage particle attaches to a bacterial cell and then injects the genome inside using its tail. The genome can either get integrated into the bacterial genome and replicate with bacteria. Or it can make virus proteins and copies of its genome. In the later case it will burst open the bacterial cell and released the assembled phage particles out in the open.

Image by Thomas Splettstoesser | CC BY-SA 3.0

That being said, bacteria also have tools to fight back and degrade the phage genome that enters the bacterial cells. I mean that is how we got the current CRISPR technology. Its always an evolutionary arms race there. Here is a post titled - Journey from adaptive immunity in bacteria(CRISPR) to saving Man's best friend(Dog). which I wrote sometime back regarding how CRISPR works. You may find it interesting.

Cominh to your second question on virus eaters. There aren't many examples of it. Its mostly like virus infects the cells and if virus fails the cells degrades its constituents and probably use it for something. Now there was some ideas floating around that some protists may eat viruses in labs, but there have not been any hard evidence for it. However recently, Brown et al., in 2020 claimed that some protists esp picozoans might eat viruses. They think their eating aparatus is too small to consume bacteria, but large enough to consume viruses of 150nm and use them as carbon source. I mean they do need more evidence. But for now I can do a more detailed journal club on why this is an interesting paper if it interests people.

Let me know if you have any further questions. 🙂