One question is: when you keep pumping the pedal does it get harder? (The pedal I mean) I understand if it's spongy or gets harder the oftener you press then you have some leak (air intake) into your hydraulic system. So find the leak ;-)
VW claim brake fluid should be changed every two years if not changed for repairs. (
https://www.myturbodiesel.com/threads/brake-fluid-and-clutch-fluid-service.36237/#post-170349).
Since I lived in Germany I change my wheels twice a year (summer - winter) and it's well worth it. Each time I change them, I inspect the brakes, looking for wear on pads and discs (and cracks on discs). If any doubt I change them - normally the whole lot as a set for all four wheels is about the same price as changing just two. The longest I leave them on is 4 years (in Germany the state 'fitness for road' test is every two years, so I change them at least every other test, in practice this has been between 25 k and 90 k km.
Since I adopted and adapted VW method of bleeding the brakes, they have been 1st class - it is REALLY worth doing it properly - it gave me a level of confidence in my brakes and my work that I had never had before.
Buy a decent pneumatic tank / brake bleeder system (spend more the first time otherwise you end up with two cheap ones that work but are not easy to use and one really good one). Buy/get at least four decent plastics bottles with appropriate tubes (5 if you want to do the clutch at the same time),
Get an assistant. Buy a 4.5 or 5 ltr Dot 6 ATE fluid (surprisingly cheap if you look around - under 25€)
'pre-bleed' them if you changed anything like a cylinder or gasket (bleed both left and right front brake at the same time, and then both rear ones).
Using about 2 bar in your pneumatic bleeder, then bleed normally in this order: front right, front left, rear right and rear left. Each time, bleed til no more bubbles can be seen.
To bleed each one: get your assistant to press brake. Open bleeder valve. Press pedal more to max. Close valve and then release pedal. VW claim do this 5 times for each brake - I bleed each one at a time and cycle through 5 times.
This seems way over the top until you have done it. Once you have done it this way once, I think you will always do it this way as you get a really solid result that makes you happy.
