Calculating old building renovation costs

Hello everyone,

I have already read quite a bit here and now I have a question myself.

We have been looking for our own house for a long time and have finally found one.

Since it is an old building from 1966, I also want to renovate quite a bit.

Key data of the house:
Detached single-family house, solid construction, 6 rooms
Purchase price €265,000
626m² plot
157m² living space
77m² usable space
2 garages
2 full floors
Gas burner is from 1993 and was recently serviced/checked. It should continue to be used for now.
Building fabric and roof are in very good condition.

The following work I want to do as soon as the purchase is completed.

The electrical system is still from 1966 and I want to completely renew it.
Remove floor coverings, screed
Insulation + underfloor heating with new screed
New windows with electric shutters.
SPS system
New water pipes
New floor coverings (tiles and parquet)
Renew bathroom and guest WC.
And of course a lot of small stuff.

I am an electrician myself and have meanwhile gained a lot of experience with a new build and an old building of friends. Therefore, I will do the complete electrical installation and programming of the SPS myself. I will also do the underfloor heating myself.
Later on, a new facade including insulation is planned.

I still have to go to the bank and arrange the financing. Equity is available, about €150,000.
However, I am still a bit unsure about the renovation costs; I roughly thought about €100,000 since I want to do a lot myself/with friends.
Is that realistic? Or do I have to make some compromises, possibly without the SPS?

If any important information is missing, just ask.

I don't know SPS. We recently wanted to buy a comparable old building and do heating/plumbing including 2 very small bathrooms, floor/painting work as well as electrical work. That came to about 100,000 euros without own labor. You probably have bigger plans and my offers are 7 months old (so completely outdated ). Your own labor is of course hard for me to evaluate.

The heating system from 1993 is basically worthless today, as AFAIK its lifespan is assumed to be 20 years. (Sure, if it still works, that's good, but regarding the value of the house or the objective modernization backlog, this heating system is simply old.)