@Gwendolene-vdm This is something you should verify with the agency to be sure, but I think this paragraph means that they are your exclusive agent (as in, you can't have another agent), not that you're not allowed to find your own work 🙂
Also, the second paragraph means that you give them permission to negotiate in your name. However, you still ALWAYS have the right to refuse any work they offer you, or ask them to request more money before accepting.
The third paragraph means that the client will pay your agent, then the agent will take their cut and pay you the rest. You do not have to pay your agent directly, the money flows from them to you.
This section makes it clear: "If you, or anyone on your behalf, directly receives any payment for your Works you shall pay the Agent’s commissions promptly." Basically the agent is supposed to receive the money directly. If the client fucks up for whatever reason and pays you directly, that's not how it's supposed to work and do still send me my commission please (I'm paraphrasing lol)
Again, double-check all of this with the agent to be sure. But I don't see anything nefarious or potentially harmful here, it all seems very normal and not as you interpreted them (unless I'm mistaken).