Arrivals at AMS are almost always at the furthest D gates, D25-D29 (or thereabouts).

If you have to pick up checked baggage: I would estimate 10 mins walk to the immigration check, 5-10 minutes waiting (or zero minutes if you have a Privium card), then onwards to the luggage claim. By then, bags are probably about to emerge, so you would probably have your hold luggage within 25 minutes of getting off the aircraft. You're better off walking back towards reclaim 20 (BA typically comes out on reclaim 4 or 6) and exiting landside there, then go immediately upstairs to the Qatar (and BA, as it happens) checkin in departures 3, which will take you 5-10 mins. At that time in the morning the security is probably fairly fast, and I expect you can use the priority lane for security and then for the immigration exit. Then exit security airside, go downstairs and head left-ish towards the G gate that Qatar is likely to use. Departures 3 and pier G are at the same end of the airport.

If you don't have to pick up checked baggage, walk from the BA arrival gate back to the main concourse and across most of the airport, then out to the G pier (where Qatar are likely to leave from) - 10 minutes speed-march, 15 minutes for a normal walk. D25 - G gate is the longest possible walk in the non-Schengen zone in the airport, so anything else will be an improvement

2 hours is possible but quite tight if you have to collect and recheck bags, try to be off the BA flight at the front. 2 hours is quite easy for an airside connection with interlined bags.