AWS S3 File Upload for existing Angular Online Form

I am a software developer currently working on an online tool for document management and a user friendly online form. The application still needs some features I am working on but due to timing issues we want to outsource the following feature:

Users fill out a multi-step online form (written in Angular 2+ using Reactive Forms). After submitting the form the data gets stored in a mongoDB database and users can check their inputs later again.

Now I want that users can upload files (PDFs, Word, xlsx, ...) from their device to that online form. The files get uploaded via an express server to an AWS S3 bucket, while the server returns the URL of the upload, which than gets exposed to the Angular form again, so that users can check the file later again.

UI elements already exists. What's acually needed:
- endpoint on existing express.js API for uploading files to an S3 Bucket returning the URL after successful upload
- endpoint on API for deleting files from bucket
- configuration of S3 Bucket on existing AWS account

I already found an article which describes almost the scenario which might be helpful:
https://dev.to/devpato/angular-with-nodejs-image-upload-to-aws-s3-easy-pec