Fixed all bugs in install.sh file

[A-Unix]

In the previous version, the script was trying to install requirements directly without checking if they were already installed or not. I've fixed that issue, even if the requirements are not installed, the script will now first check if there is any need to install requirements or not. In that way, if a user faces any error during the installation of the requirements, then, he/she can first install the requirements using the command: pip3 install -r requirements.txt and then again try to install dependencies using this modified script. Then this script will skip the installation of the requirements and give a success message after installing other remaining dependencies.