Filling / modifying land: Is approval required?

Hello forum community,

First of all, a compliment for many useful things I have been able to "learn" so far as a silent reader.
Today I am also actively joining the discussion because at first glance I could not find a 100% answer for my concern.

Situation:
During the surveying (rough measurement including staking out) of our property on which a bungalow will soon be built, we also determined corresponding heights.
In the end, it turned out that we need/want to raise the part of the property on which the house will stand.
In the first step, of course, the house area + 2.5m on each side of the house for the construction measures.
This results in an area to be raised of just under 500 sqm.
Since the heights in this area vary significantly, 7 measuring points were taken, whose greatest difference is 0.65m. (Max: 20.01, Min: 19.36)
The plan is a first elevation to about 19.80 to initially have a level and balanced surface.
On average, over all measuring points, this elevation would be just under 30cm.

Question 1 Is this permissible without further ado or do I already have to apply for a permit..!?
If yes, simultaneously with the building application still to be submitted or is the elevation already listed or taken into account in the same!?

Question 2: Since there was previously a sea of smaller trees on the property up to the removal by us, we want to remove something shortly (about 10 cm) to reach the first sand and to have new unusable bushes and co out of the way.
Is this at least allowed without major inquiries or permits!?

A few more details:
- Property is located in Lower Saxony
- is a "gap," meaning neighboring developments have existed for about 40 years, i.e. no new development area.
- Soil report is available: "Sand and topsoil"

If further details are needed for a clear statement, please let me know, otherwise I already thank you in advance for your (hopefully positive) help

30cm height increase is almost normal. I think the development plan specifies how high you are allowed to build. Usually up to 50cm or similar.

500 sqm... that will be a pretty big bungalow, if I subtract the 2.5 meters on each side.

As for the small trees: what does "smaller" mean to you? If it is scrub, here and there a thin birch trunk, and your architect hasn't mentioned anything about a felling permit or the like, the clearing probably counts as cleaning the building site. ... <- I assume that, I don't actually know [emoji2]
Have fun cleaning up!

A 30cm increase is almost normal. I believe the development plan specifies how high you are allowed to go. Usually up to 50cm or so.

500sqm... that will be quite a large bungalow, deducting 2.5 meters on each side

Regarding the small trees: what do you consider "smaller"? If it’s just scrub, here and there a thin birch trunk, and your architect didn’t mention any felling permits or the like, the clearing probably counts as cleaning the building ground. ... <- that’s what I assume, I don’t actually know [emoji2]
Have fun cleaning up!

Thank you for your quick feedback.

Ok, not expressed clearly
500 sqm not as living area but as the plot area to be worked on, since this will also include part of the garden as well as the planned driveway in the "filling measure".

I think I have read in several posts about sqm areas being used as a criterion for whether a permit is necessary or not.
Similarly, negative impacts on neighbors.
Which, in my (amateur) opinion would not be the case, since there is still at least 3m distance from the intended increase to the property boundary..!?

Yes, they were mostly thin trunks otherwise shrubs, which we have already had "felled".
That means there is now a thin and scattered shrub layer present.
As I said, I only want to remove this by a few centimeters to have a reasonably prepared surface for the remaining fill.
That should surely be possible without any problems..!?

Yes. But if you change your terrain, and as a result the neighbor has rainwater problems, then you have to take care of it and pay for it if he has to drain because of you or similar. The bushes do not matter.