We bought a set of returns of which one should have been the 6020 piece Hogwarts castle. We received 37 bags that are represented in the pics below packaged neatly in the Hogwarts box. We have bags 1-37 with no instructions and no idea which set they belong to. We might as well build it since it's here. :) Any help would be great.
I believe you have a mix of at least two sets: 11005 Creative Fun and one of either 10717 Bricks Bricks Bricks or 11717 Bricks Bricks Plates.
Bag 36 contains a Door 1 x 4 x 6 with 4 Panes and Stud Handle (Medium Blue) which was featured in 5 sets.
11003 Bricks and Eyes
10264 Corner Garage
10703 Creative Builder Box
10702 Creative Building Set
11005 Creative Fun
10260 Downtown Diner
31025 Mountain Hut
31065 Park Street Townhouse
Bag 36 also contains a Plate, Round 4 x 4 with Hole (Dark Tan) which was featured in 22 sets.
41167 Arendelle Castle Village
75958 Beauxbatons' Carriage: Arrival at Hogwarts
11005 Creative Fun
11013 Creative Transparent Bricks
80102 Dragon Dance
71730 Epic Battle Set - Kai vs Skulkin
70674 Fire Fang
41395 Friendship Bus
71043 Hogwarts Castle
76129 Hydro-Man Attack
70668 Jay's Storm Fighter
70667 Kai's Blade Cycle & Zane's Snowmobile
70675 Katana 4x4
70677 Land Bounty
70680 Monastery Training
30534 Ninja Workout polybag
40342 Ninjago 2019 Minifigure Set blister pack
75270 Obi-Wan's Hut
75937 Triceratops Rampage
70840 Welcome to Apocalypseburg!
70419 Wrecked Shrimp Boat
75255 Yoda
These two pieces have only appeared together in 11005 Creative Fun.
However, bag 32 contains a Slope, Curved 3 x 1 x 2 with Stud (Lime) which was featured in 19 sets - none of which were 11005 Creative Fun.
11011 Bricks and Animals
10717 Bricks Bricks Bricks
11717 Bricks Bricks Plates
70803 Cloud Cuckoo Palace
10703 Creative Builder Box
10702 Creative Building Set
8961 Crystal Sweeper
45810 FIRST LEGO League (FLL) Jr Challenge 2019 - Boomtown Build Inspire Set
41345 Heartlake City Pet Center
71367 Mario's House & Yoshi - Expansion Set
41339 Mia's Camper Van
60270 Police Brick Box
7676 Republic Attack Gunship
75021 Republic Gunship
21208 Resort Designer
76134 Spider-Man: Doc Ock Diamond Heist
70922 The Joker Manor
41455 Unikingdom Creative Brick Box
60125 Volcano Heavy-lift Helicopter
Bag 32 also contains a Slope 45 2 x 4 (Lavendar) which was featured in 7 sets.
10717 Bricks Bricks Bricks
11717 Bricks Bricks Plates
10704 Creative Box
41340 Friendship House
41108 Heartlake Food Market
41310 Heartlake Gift Delivery
41253 Lonesome Flats Raft Adventure
These two pieces have only appeared together in 10717 Bricks Bricks Bricks and 11717 Bricks Bricks Plates.
TLDR. Although bricks seem to be packed in sealed bags, these looks to be a mixture of parts since none of existing set inventories contain such combination of bricks.
More details below.
Based on the colors of the bricks you have received this is definitely not a Hogwarts Castle.
Let's start with contents of bag #36, since it has elements easier to identify. The combination of Door 1 x 4 x 6 with 4 Panes and Stud Handle mentioned in another answer is definitely not in Medium Blue, but some shade of Azure. Checking Bricklink for colors available for this element we can conclude this is Medium Azure colored item. Now this element come in just 5 sets, none of which have Plate, Round 4 x 4 with Hole OR Brick, Round 4 x 4 with Hole in Dark Tan. So the set this bag comes from doesn't exist.
Now let's see bag #4. Combination of Brick 1 x 2 in Coral color as well as Slope, Curved 2 x 1 x 1 1/3 with Recessed Stud in Lime may suggest this is Bricks and Animals (11011), but it doesn't include any of Slope, Inverted 45 2 x 2 in shades of blue. So no set for this bag as well.
Bag #19 again, suggest combination of Brick, Modified 1 x 1 with Stud on 1 Side in Coral color with Slope, Curved 3 x 1 x 2 with Stud in Lime suggest this may be Bricks and Animals (11011), but this set doesn't contain Plate 4 x 4 in Green.
These bags come from either set that has not been inventoried yet on Bricklink or incorrect bricks have been packaged for particular set (which might explain why they have been returned). The source of these bricks/bags would be some larger set from LEGO Classic series.
Medium Azure or Medium Blue and went with the one that I could find a plausible set match for. But the fact that I missed the color of the 4x4 tile too tells me I need to re-calibrate my monitor. +1 for catching that.