Can someone please help me understand the tax implications in Germany of the stocks and shares holdings in my ISA in the UK? I have a large pot of various index linked funds and investment trusts with Hargreaves Lansdown and AJ Bell I have made no new cash contributions within my ISAs since I left the UK for Germany in Nov 2020. I realise that leaving the ISA open in the UK leaves me exposed to £/EUR fluctuations and I have no intention of withdrawing the money in the near term, but I’m still a bit confused about the tax implications here in Germany. Do I have to declare my entire ISA holdings in my German tax return or the unrealised gains? Let's say 5 years ago I put £8,000 in my ISA, and in that time the index share price went up 25%, so I have £10,000 now. When I declare this on my German tax return, am I declaring the £10,000 or whatever the total sum is at the end of the tax year or the £2,000 of increase in value? Additionally, since 2023, I have earned interest on the cash balance held in my stocks and shares ISA (i.e. the amount not yet invested). I understand I should declare this as well, but is there anything else I may have missed?
Some more details about me:
- I came to Germany in Nov 2020 and have no plans of returning back to the UK, but I prefer not to liquidate my stocks and shares in the UK due to immediate capital gains tax implications. But is there a reason that people move everything over to Germany from the UK before retirement? Doing so means I would need to find German equivalents for my funds and also a suitable platform, which I don't know much about.
- I also have some pensions, i.e. SIPP pots, pension with my old employer. I am 45 years old and prefer not to withdraw before I’m 55.
- My husband is German citizen and we have a Lohnsteuerberater who is helping us file our joint taxes since last 2 years. The only income we have declared is from our employment and rental income from my property in the UK.
Sorry for the length and detail of this but I'm not sure who to ask about this. I realise I need to declare my ISA holdings to the Finanzamt and that I have missed doing so in the last couple of years. And that there could be a penalty for not declaring earlier. The only explanation I can give for this is: having a baby in Germany, stress of returning back to work, and severe health complications. But I am finally back to my old self and want to fix my affairs.
Thanks for taking the time to comment

Ps- I scrolled through some of the old comments in this forum but did not find any threads that really covered the above. Hence, posting here.
Thank you!
Sehar