The recognized python version different from the installed python version

I am pretty new to Ubuntu, so sorry if this question is too basic. I have followed these links to install python 3.7 on my Ubuntu 18.04.

https://linuxize.com/post/how-to-install-python-3-7-on-ubuntu-18-04/

https://docs.python-guide.org/starting/install3/linux/#install3-linux

However, once I run the command python3 --version I get Python 3.6.8. Problem is if I try again to install python 3.7 using the following commands:

$ sudo apt-get install software-properties-common
$ sudo add-apt-repository ppa:deadsnakes/ppa
$ sudo apt-get update
$ sudo apt-get install python3.7

I get

 python3.7 is already the newest version (3.7.4-1+bionic2).

which python does not give me anything, but whereis python yields to

 /usr/bin/python3.7 /usr/bin/python3.6m /usr/bin/python3.6 /usr/bin/python3.7m /usr/lib/python2.7 /usr/lib/python3.7 /usr/lib/python3.6 /etc/python2.7 /etc/python3.7 /etc/python3.6 /usr/local/lib/python3.7 /usr/local/lib/python3.6 /usr/include/python3.6m /usr/share/python

Does it mean I have all the versions? which I cannot understand, since I have installed only one python on my system.

So any ideas on what I am doing wrong? I have been suggested that this could be a duplicate of I changed my Python version - but it didn't "take" everywhere? but I think mine is a different problem cause nothing there helped me to solve my issue.