Financing cultivation, renovation with an existing loan

I have a question for clarification on how to best finance an extension and renovation (insulation + windows, drainage) of an existing property for which a loan is still outstanding.

I have no idea yet about the financing amounts involved.
The house cost €435,000, of which €348,000 was financed and approximately €289,000 is still outstanding.
The installment is €1720/month with 1.74% p.a., financed through the DKB.

There is currently equity of about €70,000 available and I do not expect any construction activities before 2024. That means by then approximately €270,000 will still be outstanding and equity will be €85,000.

What goals should be aimed for regarding the financing? 60% through a lot of equity?
Will the existing house be revalued (appreciation) and does that have an impact on the financing?
Where does one finance something like this? Same bank?

As far as I know, you can replenish the released mortgage, even in the first priority rank at another bank. Financing broker helps

As feedback for those interested: An additional mortgage loan was taken out at the same bank as a 60% financing. Interest rate at 3.75% for 15 years full repayment, naturally worse in 2024 than back then in 2018 for 20 years. Part of the expenses will be recouped through BAFA BEG EM funding with iSFP and Income Tax Act §35c, either for final work or for special repayment.

Good luck with the cultivation. Will the object then be reassessed?

The extension is finished except for some work to be done on the interior fit-out. I cannot say to what extent an appraisal was conducted before the loan was granted. We only had to submit building plans and cost estimates + the construction company's offer. After the loan is fully disbursed, the house will still be inspected (remote).