Hi Alex,
your output from your first picture shows two process that are running on the tftp-ports (PID 3485 and 4146). Pls reboot the system an check if this is still so.
Pls. send the complete output of the command "systemctl status tftpd-hpa.service"
At the end you see, where the server is looking for files and where they will be stored.
For example:
root@test:/# systemctl status tftpd-hpa.service
● tftpd-hpa.service - LSB: HPA's tftp server
Loaded: loaded (/etc/init.d/tftpd-hpa; generated; vendor preset: enabled)
Active: active (running) since Mon 2019-05-20 14:45:48 CEST; 2 months 4 days ago
Docs: man:systemd-sysv-generator(8)
Tasks: 1 (limit: 4915)
CGroup: /system.slice/tftpd-hpa.service
└─874 /usr/sbin/in.tftpd --listen --user tftp --address 0.0.0.0:69 --ipv4 --create --secure /srv/tftp
(in my case its /srv/tftp)
Maybe you have to create this directory ?
To check the firewall settings try "ufw" or "iptables -L".
Regards,
Axel