Like Niko's achievement guide says, the best way to get these achievements is to play through an hour of endless mode, and then repeating Day One for consistent burger and fries orders.

The 2000 fries refers to individual fries within an order, the quantities are:

Not including any orders from endless mode, in order to complete Burger Server, you need to complete Day One 4.5 times. You'll get this while working toward Fry Server.

In the fifth run through, the achievement should pop after Order 12 (or Order 11 if you've completed Lilith's training once). The lettuce sandwich doesn't count toward this achievement.

Not including any orders from endless mode, in order to complete Fry Server, you need to complete Day One 9.3 times.

In the tenth run through, the achievement should pop after Order 7 (or Order 3 if you've completed Lilith's training once).

*Does not count for Burger Server achievement

Make sure you check out Niko's comprehensive guide to all the achievements in the game, and how to achieve all endings / unlock everything !

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3002664525