I've re-tested this problem, it seems that now it happens only while uploading, downloading goes perfectly fine (apt-get update, apt-get upgrade) with a bit of lag while browsing websites, but at least I can browse the internet while downloading, whereas I can't view websites at all while uploading.
I've re-tested this problem, it seems that now it happens only while uploading, downloading goes perfectly fine (apt-get update, apt-get upgrade) with a bit of lag while browsing websites, but at least I can browse the internet while downloading, whereas I can't view websites at all while uploading.