General Speed up

I would like to ask how to speed up my data base specially in importing and deleting datas. Here are my current setup:

i7- 9700 16g RAM 1TB HDD

And what do you expect? I mean, your hardware is near irrelevant but how should we know what your DB looks like or even if it is structúred correctly? Was it created following the basic DB principles or does it include nonsense like text notations or binary objects? Are field lengths consistens with their use (e.g. a VARCHAR with 250 elements of which 50 max are used is of course plain rubbish)?

etc. etc. etc.

It should be pretty obvious that using data like "01hrs:12min:13sec" instead of e.g. "01|12|13" or "yes" / "no" instead of "1" / "0" can already drastically bloat your DB. Not even speaking of the dumb idea of including BLOBs instead of simply using the path to the corresponding binary source as a naked DB with 50MB of pure data is far quicker and easier to handle as one which uses 750GB because of included binary objects. And I'm not even pointing at the data integrity and data backup rules which would of course also apply here.

As Anse already pointed out in another thread, the correct use of the ON clause has huge impact on certain JOIN operations. And I just remembered a customer which had never VACCUMed (or backed up) his SQLite DB in five years (their overall access speed increased so much that the CEO thought we had actually removed/deleted data).

TL;DR: Not enough info provided. We can't say anything without knowing what we are dealing with.