You mentioned that you want to carry out the renovation yourselves, therefore also do not want to take advantage of any funding, hence the concerns ;) Ultimately, you want to have the house renovated turnkey by a professional and then only do the usual own work like painting, flooring, and kitchen installation.
With small tasks like cutting grooves, you won't save much. The electrician does that in one, maybe two days for large houses. Considering the tools you would have to borrow, you would save only a few hundred EUR but be occupied for days. You will think about every groove, the electrician just does it because he has done it a thousand times before...
And then you also have the problem that all services build upon each other. If you fall behind schedule, the craftsman cannot keep his appointments, fixed prices expire, etc.
Not a good idea...