Indoor Climbing and Bouldering, how to add?

You should be able to add them on the watch by going to Menu>Activities & Apps>+ Add and then scroll down the list to find Climb Indoor or Bouldering respectively.

If they are simply not in the list of activity apps to add, then try a hard reset of the watch (no settings or data will be lost) by pressing and holding the Light button for about 20 seconds (ignore the Assistance Alert screen) until the watch powers off, then power on again and add the apps as described above.

I'm not sure if I'm going to use them, but it's nice they are there. 

What data screens would you use with this? 

I'm guessing current time and heart rate, but what else? 

Thank you for quick answer.

I tried to hard reset it according to your instructions but without luck. There's no new activities available in the menu.

Just some other thoughts, before suggesting you do a Master Reset (but only if having these activities is really important to you). Have you confirmed the software update actually worked by going to Menu>System>About and looking to see that it shows "Software Version 9.00" on the first screen; sometimes the updates don't work for whatever reason, so you may need to try again (via Express is best)?  If you definitely do have software 9.00 just double check these new activity apps didn't just get added to your normal list of apps anyway by scrolling down the full list of apps when you press the Start button (sounds obvious, but is easily missed - I have in the past when new activities have been added in a software update, sending me in to a spin when I couldn't find them under the list of new apps to add, because they were already in the main list).

If they genuinely aren't there then all I can say is Climb Indoor and Bouldering are present and correct on both my Fenix 6X pro Solar and MARQ Athlete with software 9.00, so a Master Reset of settings (Menu>System>Reset>Reset Default Settings) may be required to clear whatever settings bug is preventing them from being shown on your watch (sadly a Master Reset will clear all settings and you'll need to set the watch up, as if new, again).  I don't think you need need to do the more extreme "Delete Data and Reset Settings" as the non display of these new activities would be down to some kind of error in the settings config on the watch.

Thank you for your answer. I appreciate it! Unfortunately, it didn’t work. 
If I look among the available activists in the Garmin folder while it’s connected to my computer, I can’t see any new .fit files. I guess the last solution is master reset it. 

KrapfenKringel said:

What data screens would you use with this? 

I'm guessing current time and heart rate, but what else? 

Ascent/Descent would be good, and perhaps calories and load.

Keep is simple, with just those 5 datafields on a single screen. It unlikely you'll want to switch between different datascreens while climbing.

Delete data and reset settings worked. Hard resetted everything. Now I got it. Thank you!

It's a shame it had to come to you doing a Delete Data and Settings, but something must have got messed up in the settings files inside the watch at some point in the past.  Whilst it's a pain to setup the watch from scratch (and trying to copy old settings files back can just bring back the problem), a factory reset is often is the only way to sort a persistent problem out.  Glad to hear it's working for you finally!

I really like the graphical evaluation of routes I finished successfully and those I didn't. 

A color scale used by some indoor boulder halls would be cool, but then I would have to explain the app what color is what. Maybe to complex to add that.

Also recording the height during the activity could be fun. 

Also in my 7 day statistic it's listed a "stair climbing".