IIRC Bitcoin Core does not download the blockchain synchronously with the processing. It will download blocks as quickly as possible, minimally check them, and store them to be processed later. So what likely has happened is that the entire blockchain has been downloaded, but since your node is still processing them, you aren't synced yet.

There is a significant difference between what your browser is doing and what Bitcoin Core is doing. Core is not just downloading data; it is also verifying every single block and transaction and writing them all to disk. That means that there are multiple bottlenecks, not just network. You could have a CPU, RAM, or disk bottleneck. Given the specs of your machine, I am not surprised that it is taking so long to sync; your computer simply is not powerful enough to sync quickly. You have a low powered CPU and not a lot of RAM so it is going to take a long time. 4 GB RAM is barely enough, but your dual core CPU at 1.6 GHz is also going to slow you down. Unfortunately, there isn't much that you can do except wait.

I think the 4 GB ram could be a big limitation if you're also running other applications. Try closing as much applications as you can when you're not using your computer, and let it just run Bitcoin Core for a day (or night).
See if that speeds things up.

I've been running Linux on my i3 with 4 GB memory and swapfile on SSD for a long time, and I usually closed Bitcoin Core to save memory when I didn't need it. Until I added 8 GB more memory, that solved everything. I don't need a swapfile anymore, I can keep Bitcoin Core running without slowing down anything. If at all possible, you'll love a memory upgrade.

What computer specs do you have? If your computer is very limited on memory/CPU, it will indeed take many weeks to download and verify 129 GB of blocks.