Dwarf Gourami With Betta?

No, a dwarf gourami isn't suitable. Three reasons - they are related to bettas and the two species usually fight; your tank is already overstocked; and the tank is not big enough for a dwarf gourami. They need around 56 litres not 25.

I hate to tell you this, but you have fish not suited to your tank, and the tank is overstocked - the commmunity creator on here says you are 180% stocked for the size of the tank.

Male guppies - OK in a 25 litre tank, though you may have trouble down the line with the betta mistaking them for other male bettas
Betta - fine in a 25 litre tank
Amano shrimps - fine in a 25 litre tank - though bettas have been known to eat them

Then the problem fish:
Siamese algae eaters need a tank at least 120cm long
Dwarf chain loaches need to be kept in a group of at least four and a tank at least 75cm long.

To be honest with you, I wouldn't be looking to add more fish but on rehoming some. You should be OK with the shrimps, betta and guppies unless the betta suddenly decides to take against the guppes or eat the shrimp. The tank would be fully stocked with just them
But you need to find a more suitable home for the SAEs and loaches.