Lubuntu 18.04 LTS - Is it the case to enable or install a firewall?

[ubu112]

I have an old Acer Aspire One AOA150/ZG5,with only 1 Gb of RAM.I have a firewall already enabled on my router.

I read this: https://wiki.ubuntu.com/BasicSecurity/Firewall and much more about security.

I'd like to have an opinion,considering I'm using an old and weak computer, if it's the case to enable or install a firewall.That I've never used before.

If,yes, will a firewall slow down my connection speed that is only 40+ (wireless)?

Which of the three solutions,described in the link above,would be recommended ? and,especially,because I'm not an expert,the settings described are OK?

Thank you

[deadflowr]

Thread moved to Security

[thenailedone]

As nobody has replied yet I will give my 50th of a dollars worth: The most common suggestion I always say was to install ufw if not already installed and use it (there should not be any additional overhead because all this does is ensure which ports are open and which are closed). gufw is a nice GUI to make toggling it on and off easy.

[mohicann]

I would do the same. Because it's not worth not doing it.