Converting google sheets formula to excel

I agree with HansVogelaar that a sample sheet would be helpful but I do see a couple things:

=IFERROR(
   IF(VLOOKUP(B4,FILTER({$B$3:$B3,$I$3:$J3},$B$3:$B3=B4),2,1)>0,
     ROUNDDOWN((SUM($I$3:$I3))*1%,1),
     IF(VLOOKUP(B4,FILTER({$B$3:$B3,$I$3:$I3},$B$3:$B3=B4),2,2)<0,
       VLOOKUP(B4,FILTER($B$3:$I3,$B$3:$B3=B4),8,1)*-2,
       IF(VLOOKUP(B4,FILTER({$B$3:$B3,$I$3:$I3},$B$3:$B3=B4),2,2)=0,
          VLOOKUP(B4,FILTER($B$3:$I3,$B$3:$B3=B4),2,1)*1
       )
     )
   )
 )

so I think the problem is the FILTER({...} ...

you can't create a set of ranges like that.  Just filter the entire range and pick the column accordingly.  I also tried to simplify the whole equation by checking the sign of that result instead of <0, =0 and >0:

=IFERROR(
   CHOOSE(SIGN(VLOOKUP(B4,FILTER($B$3:$J3,$B$3:$B3=B4),8,1))+2,
      VLOOKUP(B4,FILTER($B$3:$I3,$B$3:$B3=B4),8,1)*-2,
      VLOOKUP(B4,FILTER($B$3:$I3,$B$3:$B3=B4),2,1)*1,
      ROUNDDOWN((SUM($I$3:$I3))*1%,1)
   ),
   "error"
 )

that said there are a couple other things I question:

a) in the VLOOKUPs the last parameter was a 2 in a couple cases when that is really a true/false but I assume any value will come back the same as true

b) in the <0 case you are returning a lookup from column I (3rd parameter is 😎 but the =0 case you are returning from column C (3rd parameter is 2), is that supposed to be an 8 also?

c) you have an IFERROR()  but I didn't see it being used so I added a "error" statement because excel doesn't allow nothing (but apparently sheets does)