Internet not working in Ubuntu (terminal)?

Question

linux

Hi
Recently installed Ubuntu 16, the second system.
Internet using Yota 4g modem.
On Windows it works fine.
It also works fine in Ubuntu, but only in browsers.
When updating the system from the terminal, it works terribly, as if I'm sitting with gprs. It also works terribly in the Program Installation Manager.
I'm new to Linux myself.

Answer 1

Install speedtest-cli:
Then, actually run it:
If the results correspond to the speed of the provider, then the problem (more precisely, not a problem, but the fact of geographical remoteness) is in the mirrors used. In this case, go to the /etc/apt/sources.list file and change it there, for example, to
Thensudo aptitude update

Answer 2

Try

git clone https://github.com/jblakeman/apt-select
python apt-select/setup.py install
apt-select -с

if you are in the CIS
In general, if you are in the same CIS, there are local networks that Yandex supports, then in /etc/apt/sources.list

deb http://mirror.yandex.ru/ubuntu/ xenial main 
deb-src http://mirror.yandex.ru/ubuntu/ xenial main