Hi, I started a full node 20 minutes ago. I forwarded port 8333 tcp and the download is very fast. After 20 minutes I was at block
135100 
I download around 300 blocks per second is this normal with a 400Mb/s Down and 40Mbs Up connection ?
Yes, It goes amazingly fast to start with and then botttlenecks from about the time I starated (2015). The last years' worth of blocks are really slow also.
Your computer is fairly fast though as it seems so it shouldn't take you longer than a few days to get the entire blockchain.