Approaching the building, I was wondered to see an old-looking facade with a lot of stonework oin it.

or "As I approached the building"
"wondered to see" sounds a little quaint. You could also say "wondered at the old-looking facade." hnnh0001's correction is good too, it sounds more conversational
I think "its facade" is better than "a facade" to specify it belongs to that building specifically, but having "it" twice in the sentence makes me want to completely reword the sentence, maybe "its old-looking facade built from mountains of stone"

This is not what you imagine when you think about theof a high-tech food manufacturing company.

Alice, the administrator and my guide for today Alice met, met with me and our first port of call was the laboratory.

Fortunately, I washad arrived at the time becausjust in time to see scientists and software engineers huddled around thea device which was looking falooked similiar to thea TV.

"Fortunately, I had arrived at that time, because scientists and software engineers were huddled..." is grammatical, but it sounds off to me. "It was fortunate that I had arrived at that time, because..." would sound better, IDK why...

InAfter a half of second sounds of applause filled the room.

or "After half a second"
"in a second" sounds more like something occurred during the time span of a second

Mission accomplished, I thought.

It is grammatical to use quotes for thoughts, like: "Mission accomplished," I thought.
In casual writing, it's fine to omit the quotes, but we still tend to keep the pause (represented by a comma)

A piece of a cake was showing on the table ofscreen of the device.

Alice said: "Imagine that you are coming back home after a hard day onf work, and then at the touch of thea button, a gourmet meal appears in front of your eyes"."

MyHer next point was a small presentation about food safety,; because this manufacturing process is not so simple in case of the, there is a risk of contaminating food byfrom the mechanical parts of this machine.

or "risk of food contamination from the..."

PThe possibilities of 3D printing the food seems endless and it may not be so long before you will sit at thea restaurant where the chef is a computer.

Approaching the building I was wondersurprised to see an old-looking facade with a lot of stonework on it.

This is not what you imagine when you think about thea high-tech food manufacturing company.

AThe administrator and my guide for today Alice, met with me and our first port of call was the laboratory.

Fortunately, I was arrived at the time becausjust on time as the scientists and software engineers were huddled around thea device which was looking falooked similiar to thea TV.

In a half ofa second sounds of applause filled the room.

A piece of a cake was showing on the table ofscreen of the device.

I'm not sure what you mean by the 'table' of the device actually. You had referred to the device earlier as something that looks like a TV, so perhaps you mean on the 'screen' of the device.

Alice said: "Imagine that you are coming back home after a hard day onf work and then at the touch of thea button, a gourmet meal appears in front of your eyes".

My next poinNext was a small presentation about food safety, because this manufacturing process is not so simple in case of the risk of. Due to the risk of food being contaminating fooed by the mechanical parts of this machinee machine, the manufacturing process was rather thorough.

PThe possibilities when it comes tof 3D printing the food seems endless, and it may not be so long before you will sit at thea restaurant where the chef is a computer.