Gap in Poroton T9

Hello everyone....
a little about me...

I am a nurse and had absolutely no experience with building.

Currently, I am building a single-family house for us out of Wieneberger Poroton T9.
I do not have a contractor by my side and my architect knows about planning but less about implementation,
So far everything has gone great, but since I am not a professional, quite a few questions have arisen which I have luckily been able to overcome until now. Now I am hearing various statements...
Anyone who knows the T9- 36.5 cm brick knows that when cutting, corners often break off because it is quite unstable inside. Now I have some areas in the masonry that have gaps of about 3-4 cm.
How do I close these gaps? My architect says to fill them with thin-bed mortar because they contain "Styrofoam" and are also insulating (which I can't really imagine)
I wanted to fill the gaps inside with foam and fill them with mortar from outside and inside. If that is correct, should I foam the insulating foam as far out as possible or inside? And which foam do I best use?
Or are there better alternatives?

The roof is already on, windows are coming next week. Now I want to close the house completely...

Thank you very much for the upcoming help

Could you upload a few photos, that would be very helpful.

Respect! I would listen to the architect. Back when I used to lay bricks so playfully myself, I would have definitely worked a suitable piece of brick into the 3 to 4 cm thick gaps. But, ideally, the architect should know best (if no bricklayer is involved). Photos would of course still be interesting!

Construction foam inside the wall is not quite so good (either completely outside or completely inside). Inside, if at all, then possibly well foam. The problem is that the moisture absorption and release of ordinary construction foam (e.g., through capillary action) is different from that of the stone. Depending on your wall structure, it may happen that the dew point will not be far from the foam, then condensation problems can occur. Thin-bed mortar is way too liquid, it just runs out again. Just mix mortar (Speis) in small quantities and seal the openings on the outside and inside. If the openings are too large, work in remnants of other stones. Air inside the wall is not bad; on the contrary, air is a poor heat conductor.

There is special insulation mortar after all. Wouldn't that be the means of choice? That's how I would do it anyway.

To upload a photo, the file is unfortunately too large ... But thanks already for the answers.