The script is complaining that it can’t find curl? What is this script that you are using? It’s probably got a super-basic check for curl (in the wrong location) that can be modified. (Type in the source URL for it here, or something.)
However, running any script without fully understanding it is not advisable to begin with.
Typing in ‘which curl’ at the command line should give you the proper location of the existing binary of curl.
There are about a million different flavors of how to download and execute a shell script. Regardless, you need to redirect the output of curl into bash with the -s flag. Bash needs to know that it is reading from STDIN.
Here is an over-thought stackoverflow page on it: https://stackoverflow.com/questions/5735666/execute-bash-script-from-url
Also, if the script is not being read properly, that might explain the dpkg lock issue. Running two instances of dpkg simultaneously is likely causing that collision you are seeing. (If one instance is running, it will touch a lock file and then delete it when it stops. It prevents “bad things” from happening when two instances of the same app want the same resources.)
That is odd if your path is broken. It curl should be in /usr/bin and ‘which’ should find it. Are you somehow launching another shell inside a shell? Like zsh inside of bash, or something in that flavor? (In some rare cases, that would break paths and profile configs for your active shell.)
Regardless of why curl isn’t being found, or only partially found, or something, learn “env”. You need to get a decent picture of what your working environment is and why something as basic as curl “isn’t found”. (‘which’ is about as a baseline of a command as there is.)