If u are a traveller and not a tourist and visiting not just for a tick box exercise I suggest 8 days should be sufficient to cover one country. go to Turkey - visit Istanbul, cappadocia, izmir, Anyalya. and trust me even 8 days wid not do justce to one country
Europe is a continent with so many countries in it. if you are a first time traveller and and prefer to travel thoroughly then I will suggest France (paris-nice-monte carlo), or you can club France and Amsterdam. then you can club France and Switzerland for 8nights
For Switzerland you can cover lucerne half day and then go to Interlaken . then you can go to Titlis mountain and ryan falls another day . if you have more time you can visit jungfrau mountain as that is the highest peak of europe. Worth visiting. Then you can go to zurich too .city tour from hourly boats which are covered in your train ticket is worth experiencing.