Google Cloud speech-to-text is an API that returns a transcript of an audio file. https://cloud.google.com/speech-to-text/docs/quickstart-gcloud is a quick start guide of the API. The API supports some English accents fully and Dutch. There are several how-to guides at https://cloud.google.com/speech-to-text/docs/how-to, there are guides for transcription, detecting language and separating different speakers.

AWS has Amazon Transcribe which has (the free Tier is 60 min per month so this may not work well for a student project where prototyping and testing are on a short time frame but more intensively). Take a look at the get started guide, with additional links to more information. This AWS service requires a credit card for free use.

In IBM cloud there is Speech to text via the speech to text service (add it via Catalog) see the getting started guide. Dutch is supported and the lite plan has 500 minutes per month.

Microsoft has Speech to Text under cognitive services, this services documentation can be found here. Dutch is supported and the free Instance has 5 audio hours per month.

DeepSpeech is an open-source option that is developed by Mozilla, but seems to be no longer maintained. See the GitHub and tutorial for more information. The documentation can be found at https://deepspeech.readthedocs.io/en/r0.9/. A more recent fork of this project is actively developed and maintained by Coqui AI STT, which might work better on newer OS and hardware versions.

If you wish to easily compare and use various online/offline ASR tools in one package, you could consider using a wrapper like Uberi Speech Recognition, which abstracts away much of the underlying API's by offering a common speech recognition interface.

Once you have your transcript you can apply sentiment analysis or other NLP components.