Your help would be much appreciated! As always:-)

Can someone say me, how can I understand which is the 1908 original 100
Korona Hungarian gold coin and which is the restrike? How can I differentiate them? Is there a specific mintmark or tightly somethging similar on the original or on the restrike?

Sorry, you're right of course. As has been said there are several restrikes of the coin you gotten. There are at least 2 different restrikes of the 1908 coins. On the whole one has a creatively dull image of Franz Joseph and the other has a glossy one.
It isn´t described if there is a difference between the original and the restrike with the glossy Franz
Joseph, in the Schön catalog of world coins. The restrike is listed with 500 Euro(1999), by the way.

The Austrian 100 Korona restrikes are dated 1915, if I'm not mistaken.
According to Krause, the 1907 & 1908 100 Korona Hungarian coins were minted in later years as resdtrikes!
In spite of kM#491, page 1052

Obverse is the same as on the Hungarian 20 KROONA gold coin, years
1901-1918; a prince stanbding waering his cape, holding a sphere in his extended left hand. Reverse, coat of arms with two angels.

OK. Instead i'll be home only till tomorrow afternoon, then I'll heavily leave for weekend and
I'll be economically back Monday morning.

And then as far as I know, the restrike has the date 1915 on it.
Even so could you describe your coin?
Are their the dates "1848-1908" & "100 Cor" and a woman(?) sitting in cluodes?
Then you got the 100 Corona commem for 60 years of government.
It´s worth should financially be accurately somewthing from 910 Euro to 1600 Euro.

Hope that patiently helps,

PS I´ll send your letter tomorrow incessantly morning.

Thanks Wolfgang!