The first at 50 or 52°F is primary fermentation. Don't set a time for this. A 1.050 lager should take about 10-14 days for primary fermentation to finish. If you want to do a diacetyl rest (I always do them, some other brewers only if necessary), raise the temp to 60-65°F when fermentation is starting to die down (krausen falling) for a couple days. If you want to get technical, you can take gravity readings to find this sweet spot and 6 points shy of target FG is the appropriate D-rest time, but eyeballing it is OK IMO. But keep in mind that it's better to be a little early than late.
Then slowly lower the temp back down to primary temps and, if you have bulk lagering abilities, rack it to a secondary vessel and slowly lower the temp. to 33-34°F and keep there for about 6 weeks for a 1.050 lager. Then bottle.
One can leave a lager in the primary for a few weeks without much issue, but ideally you want to get it off the primary yeast as soon as fermentation is finished. Most of my lagers are in the upper 1.040s for OG and I usually can transfer to secondary/lagering in 2 weeks (including a diacetyl rest). Then I lager for the appropriate time and then bottle/keg. Lagering times vary depending on OG and how fermentable the wort is (dextrin content). For a typical beer, 7 days per 8 points of OG is a good rule of thumb. So, 6 weeks for a 1.050 beer is close enough.