Hi @Kasirajan,
I think your problem could be a misunderstanding of what this documentation is referring to in terms of Unix paths.
./getssl means to run the getssl program from the current directory, so if you’re using getssl, you have to cd to whatever directory getssl is installed in before running that command. It won’t work if you’re in any other directory.
sudo ./path/to/certbot-auto does not mean to literally type the string ./path/to/certbot-auto. Rather, that is supposed to be replaced by the particular directory path where certbot-auto was downloaded on your system.
In both cases, the documentation assumed that you know what directory the program is located in (because you would have previously downloaded it yourself), and is asking you to specify the appropriate directory in order to run the program. This is common for Unix software that you download yourself, because you’ll have a choice of what directory to save it into, and that directory is probably not in the default PATH and therefore needs to be specified explicitly when running the software.
Also in both cases, renewal instructions are probably assuming that you previously used that same software to obtain your original certificate. So a relevant question is exactly how the original certificate was obtained (by running what command).