7 days in Switzerland comming from Milan.

Beginners confusion.
First look at a map. A map of the Swiss rail network is here: https://www.sbb.ch/content/dam/sbb/de/infotexte/uebersichtskarte-sts.pdf
Print this out and plot your route on it.
All the red lines are rail routes. This map shows most routes (except in some cities), but not all stations due to lack of room. Each and every rail route has at least one train per hour in each direction.

For detailed rail times, see the SBB website: https://www.sbb.ch/en/

"how to plan The train schedules" - don't need to, there will be a train every hour.

"Bernina Express makes stops along the way to Pontresina?" - this is not one train, it is an hourly service - the "Bernina route". There are lots of intermediate stops. If you look on the map, you can see Pontresina shown.
If you want to go from A to X, look up A to X on the SBB website. The website includes all transport (train+bus+lake boats+cable cars+city transport).

"Glacier express to lauderbrunnen" - again, it is a route with one train per hour. The Glacier Express route is Chur (or St Moritz) - Disentis - Brig - Visp - Zermatt (with many other stops). Nowhere near Lauterbrunnen. If you want to go to from Pontresina to Lauterbrunnen, look it up on the SBB website. This will always find the quickest route. If you want to force another route, add a "via" (e.g. via Brig), or look it up as two searches.

Relax, and enjoy your trip.

Are you looking to do a mini "Grand Train Tour of Switzerland"? Much of the time spent riding scenic trains?
If so, it could look something like this from mid June onward.

10:20 regional train from Milano Centrale to Tirano, arrive 12:52. Then 1 hour for lunch in Tirano.
14:07 Bernina Express to Pontresina, arrive 16:04. Then 2 nights.

9:02 regional train to Samedan, arrive 9:08
9:25 Glacier Express to Brig, arrive 15:40.
From Brig, you have a choice of the fast way, under the mountains with the Loetschberg Base Tunnel.
15:48 IC train to Spiez, arrive 16:24
16:33 IC train to Interlaken Ost, arrive 16:57
17:05 regional train to Lauterbrunnen, arrive 17:25
Or take a slower scenic route over the mountains through the old Loetschberg Tunnel.
16:36 regional train from Brig to Spiez, arrive 17:44
18:05 regional train to Interlaken Ost, arrive 18:28
18:35 regional train to Lauterbrunnen, arrive 18:55
Then 3 nights exploring the Berner Oberland region.

Then pick any of the hourly connections from Lauterbrunnen to Luzern. Trains are always at 32 past the hour and arrive in Luzern, after a train change at Interlaken Ost, 2 hours and 23 minutes later. The train to Luzern is the eastern end of the Golden Pass line over the Brunig Pass.

There is one direct train from Luzern to Como S. Giovanni station and many with a connection in Arth-Goldau. These use the new Gothard Base Tunnel. Fast, but going under the scenery in a 35 mile long tunnel. But since this is a scenic excursion, you have the option of taking the Gothard Panorama Express. It starts with a lake cruise boat to Fluelen, than change to a train that uses the route with the old Gothard Tunnel that goes mostly over the mountains. At Lugano you change to a train to Como.
https://www.sbb.ch/en/leisure-holidays/travel-in-switzerland/panoramareisen/gotthard-panorama-express.html

The Bernina Express, Glacier Express, and Gothard Panorama Express require supplemental seat reservations. I believe to ride panorama cars on the Gothard Panorama Express, you need to book 1st class. the others have 2nd class panorama cars available.

Thank you for your assistance. Would u advise me to get the travel Swiss train pass or the point to point. I understand that the swiss travel pass includes the Bernina Express train and the Glacier Express with additional fee for reservation fee. For those 2 trains you need exact time of travel. Can that be possible if u are also using other public trains? I'm traveling mid may

Would u advise me to get the travel Swiss train pass or the point to point.

Sorry, but the only way to work it out is to list all your trips (in a spreadsheet) and add them up. There are actually THREE options:

• Swiss Pass, nothing further to pay apart from some mountain cable cars, which are discounted.
• Half Fare Card, plus pay half price for all tickets.
• Pay full fare for tickets.

Whichever you choose, the trip from Milan to Tirano requires a separate Italian ticket, but these are cheap.

I understand that the swiss travel pass includes the Bernina Express train and the Glacier Express with additional fee for reservation fee. For those 2 trains you need exact time of travel. Can that be possible if u are also using other public trains?

Not sure what you are asking here. The Bernina Express train and Glacier Express are extra trains over and above the normal hourly trains on the same route, and require reservations whether you have a pass or normal tickets.
You only need "exact time" in as much as they only run 1-2 times per day, and your reservation would be for a specific train.
If you need another train to get to or from the place where you join or leave these trains, then your pass or normal tickets are valid, just use any train.