allright, I am not going to do your work, of course, I believe I would not be helping you as you need to learn in the first place. But, here is a very good kicking off.
As you can see the PC7 can access the internet, which is a WWW server on your Data Center. PC7 is also using IP address from a DHCP server in the Data Center and in order to access the internet, it is using a DNS server in the Data Center.
With that, you can achieve a few step from the assignment.
There is a "router in a stick" proper configured between the switch, where PC7 is connected, and the router inside the Data Center. The way you created router in a stick is wrong.
For router in a stick the switch does not have interface vlan wth IP address. The switch is only layer2 device on this case. The layer3 stay on the router side.
You now have OSPF running between the router and the Core switch inside the Data Center. You just need to replicate that to the other routers.
As you can see, I changed your design. You were connecting site to site and we dont do that in real world. We connect Site to Data center.
You can, eventually, connect the site to another router inside the Data Center for redundancy BUT, it would complicate the project and they are not asking this.
So, my proposal for you is, now, you replicate the configuration I did for the site in Blue area, to other sites following the same principle.
Look closely on how I created the router in a stick, starting by looking the switch config. Then, how I connected the router to the Core switch on the Data Center, how I built the OSPF adjagency.
You also need to create the remaning DHCP scope on the DHCP server inside the Data Center. It is pretty easy to create DHCP scope. Just organize your networks segments accordingly.
For Area Blue, I used 192.168.10.0/24 and 192.168.20.0/24. You keep going with the sequence for other sites.
Good luck and you can ask for spefics but get busy because there are a lot of work to do.
