In Pathfinder 1e golems have a Magic Immunity which apparently makes them immune to all spells that allow Spell Resistance.
So how to defeat those? An obvious answer would be a buffed up fighter or something to destroy it. The catch is that we're playing as a group of only spellcasters (Witch, Wizard, 2 Sorcerers) so that's not really an option. What spells or other things can we use?
If you say spells that don't allow SR then please be specific with some actually good ones because I can't really find any. Note that we're playing at rather high level with lvl 5-6 spell slots now.
Another possibility might be summoning but most summoned creatures seem rather weak so they would have trouble with overcoming the golem's DR – so again be specific if you want to suggest summoning.
What else?
Best Answer
Ignore them
No golem in the game presents a threat to an 11th level full caster, nor to their slightly weaker T2 cousins. This, the Adamantine Golem, is an example of a theoretically top-tier Pathfinder golem. Note its 30-foot movement speed (for a maximum typical travel distance of 120 feet in a round, no better than default) and lack of ranged attack options. Note its inability to receive the vast majority of standard buff spells due to its magic resistance, coupled with its complete lack of feats or even skill ranks due to being the bad sort of mindless.
Your witch and wizard could cast communal mount (and the sorcerers might know mount via pages of spell knowledge or for real because they were a summoner back at level 4ish), but you could also buy normal horses instead with money and money is less valuable than spell slots so do that. Then ask (or ask) your horses to run away from the golem. Crisis averted.
Your wizard could cast hungry pit, which the golem's +9 reflex save is not enough to consistently avoid since it needs to repeat the save every round and your DC should be over 20. That leads to the golem falling down a very deep pit and then being chewed up at the bottom with no chance of escape while you safely attack it from afar (e.g. by burying it under several thousand pounds of molten lead). You could also dig the pit with mundane shovels (or have your servants do it), and then just get it fall in nonmagically-- its total perception score is +0.
You could cast overland flight and then do whatever. It can't move as fast as you, it can't fly, it can't attack at range, and your spell lasts ~11 hours.
Maybe, though, you are concerned about running into one in a confined space, like a dungeon? Recall that you have access to teleport.
But maybe it's threatening to do something bad other than harming you and stopping it is really urgent and it doesn't have to go anywhere out in the open to do that? Disable Construct should have an about-even chance of putting it out of commission on each of its castings, and the touch range can be bypassed via Spectral Hand.
Or Acid Fog which is solid fog but plus 2d6 damage per round, or other irresistible damage-dealing spells-- check pathfinder Mailman builds (most use either snowball or storm of blades, you could mix in flurry of snowballs if People of the North is replaced by Ultimate Wilderness, but it's a lot less good).
Or summoning: lantern archons, lillends, shadow demons, chaos beasts, bralani, and probably others can defeat most golems in relatively short order. With Heightened Mount plus Alter Summoned Monster you can have the summoned creatures around all day rather than for a minute or two, and you can refresh their SLAs or change them to another sort of summon entirely with another Alter Summoned Monster.
Or diplomacy, if you have Axiomatic Discourse: just because you're mindless doesn't mean you aren't a creature. And there's lots of spells that boost diplomacy.