@dogacet I edited your post. Please, follow tips in the following post next time to help us by making your post more readable and get an answer more quickly.
Luckily for you, @rofrano gave you great advice even without formatting. I just want to add clarify some possible misunderstaning.
Actually both 127.0.0.1 and 172.20.0.3 is an IP address inside the container. 127.0.0.1 works, because of port forwarding. In other words: publishing port 80. Then host machine has its own loopback IP 127.0.0.1 and port 80 is forwarded from that IP into the container in the virtual machine. One of the jobs of Docker Desktop is to forward ports from the host to the virtual machine, so Docker inside that VM can forward the port from the VM into the container. The IP address 172.20.0.3 does not exist on the host machine, because that belongs to a local, private interface inside the VM. That is why it doesn’t work. Applications running inside the container do not know anything about the IP addresses of the host machine, at least not in case of Docker Desktop, so you can’t rely on the information shown in the containers’ console.