Heroku git push rejected

Question

I am a learner at the very beginning and I am having an issue with an app I am supposed to host on Heroku. It is an MERN app, not yet complete, but so far, functioning.

I did the initial proceedings to commit the whole app to Heroku, but instead of making the git push heroku master I was supposed to do, I did a simple git push. When I tried to do the push properly, Heroku rejected it saying that it had failed to push some refs to... the correct Heroku git url.

Following a great deal of searching, a colleague recommended me to delete the app and start from scratch and so I did. The issue then is that this new app, made all from scratch, after carefully deleting any remains of the old app is bringing me the same outcome after the command git push heroku master, which I post here:

Enumerating objects: 1417, done.
Counting objects: 100% (1417/1417), done.
Delta compression using up to 8 threads
Compressing objects: 100% (1347/1347), done.
Writing objects: 100% (1417/1417), 684.11 KiB | 5.07 MiB/s, done.
Total 1417 (delta 528), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote: 
remote: -----> Node.js app detected
remote: parse error: Expected separator between values at line 8, column 11
remote:  !     Unable to parse package.json
remote: 
remote: 
remote: -----> Build failed
remote: 
remote: We're sorry this build is failing! You can troubleshoot common issues here:
remote: https://devcenter.heroku.com/articles/troubleshooting-node-deploys
remote: 
remote: If you're stuck, please submit a ticket so we can help:
remote: https://help.heroku.com/
remote: 
remote: Love,
remote: Heroku
remote: 
remote:  !     Push rejected, failed to compile Node.js app.
remote: 
remote:  !     Push failed
remote: Verifying deploy...
remote: 
remote: !   Push rejected to morning-lowlands-64044.
remote: 
To https://git.heroku.com/morning-lowlands-64044.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to [Heroku Git URL]

I am unaware of any other relevant inputs. Could someone tell me which path to head to? I don't mind doing it everything again if needed, but I don't want to start doing anything without a minimal level of certainty to avoid making the problem worse. If more input is needed, I will be glad to provide as well In advance, thanks to all and have a nice afternoon/evening.