Can you replace a battery with a higher amp hour than the one that was in it ex 12v 28ah with a 12v32ah?

How you connect 40Ah and 28Ah batteries of same voltage?

It depends on the voltage you wish to use - if the voltage is, say 12 volts (and matches exactly), you could place in parallelel for 12 volt output, and the ability to serve more current. If you want 24 volts, put them in series. If you do place them in parallel, note the 28Ah battery will discharge sooner than the 40Ah, causing the 28Ah battery terminal voltage to drop, which will cause the 40Ah battery to attempt to charge the 28Ah battery up to the full voltage again.