1
We finally reached an agreement.
To sign this, you would start by signing 'WE' and 'FINALLY.' Then, perform the sign for 'AGREEMENT' by touching your forehead and bringing your parallel index fingers together. This clearly shows that after some time, everyone has come to share the exact same thought or perspective.
2
I am in agreement with your plan.
Begin by pointing to yourself to indicate 'I,' then use the sign for 'AGREEMENT' to show your shared mindset. Follow this up by signing 'YOUR' and 'PLAN.' This sequence effectively communicates to the other person that your thoughts align perfectly with the ideas they have proposed.
3
They signed the agreement yesterday.
Start by establishing the timeline with the sign for 'YESTERDAY,' then point to indicate 'THEY.' Next, use the sign for 'AGREEMENT' to show the shared understanding, and optionally add the sign for 'SIGNATURE' or 'PAPER' if you want to emphasize that it was a formal, written contract.