NFS: this VM is both s1, the server, and s2, the client: it mounts its own export through 10.99.0.1, the way another machine would, so the server sees the client as 10.99.0.1. That's s2's address here. The traffic never leaves the VM. The lab orders the NFS server before network mounts, so the mount comes up at boot and goes down first at shutdown.
Samba: the peer is s2, the client. Run its commands with sudo ip netns exec lepeer, for example sudo ip netns exec lepeer smbclient //10.99.0.1/docs -U dana -c ls. Its traffic comes in over le-host, so open the firewall for Samba if it's running.

The lab installs smbclient, and creates users pat (the same UID on both machines, since they share their users), dana (in group docs) and eli (not in it), all with password Lab-Pass-1.

Tasks

On s1, export /srv/projects read-write to s2 (10.99.0.1) only. On s2, mount it from 10.99.0.1 at /mnt/projects at every boot. showmount -e 10.99.0.1 lists /srv/projects with that address, and findmnt /mnt/projects shows type nfs4.
Make the export writable for pat, but not for root on s2. As pat, touch /mnt/projects/f works and ls -l /srv/projects shows the file as pat's; sudo touch /mnt/projects/x fails with "Permission denied", because root counts as nobody.
On s1, share /srv/samba/docs as docs, writable only by members of the Linux group docs, and give the member dana the Samba password Lab-Pass-1. testparm -s shows the [docs] section; from the peer, dana can list the share and put a file there, and eli (who has no Samba password) gets NT_STATUS_ACCESS_DENIED.

Hints

apt install nfs-kernel-server; /etc/exports (no space before the parentheses), exportfs -ra, exportfs -v, showmount -e; a line in /etc/fstab with _netdev, then systemctl daemon-reload, mount -a.
root_squash is the default; chown, chmod 755; su - pat.
apt install samba; a [docs] section with path, valid users = @docs, read only = no; chgrp docs, chmod 2770; smbpasswd -a, pdbedit -L, testparm -s, systemctl restart smbd. ufw allow Samba.