Your enlarger or some part of it is, no doubt, defective, the possibilities ranging from the bulb (wrong voltage, wrong wattage, wrong type) to lens (malfunctioning aperture) -- and the entire lightpath between them. Your light seems at least about three stops too dim. It's quite much. Don't try to get a brighter lens, instead find help to fix the actual problem. It's probably something obvious for someone familiar with enlargers. They are not so complicated.
There are many things mentioned but has anyone mentioned the bulb voltage yet? Check it. If the bulb is for double voltage than the enlarger, that would explain the problem. Halving the voltage may be about two stop loss in light output or even more. And it's always possible that the enlarger gives wrong voltage, different than specified. Measure it if you have access to a volt meter. Or maybe the enlarger has 220V/110V switch and it's at the wrong position. It's easy to check - open the bulb compartment and switch the light on - it should be white and so bright that you almost feel pain in your eyes . If it's a little orangish and lame like the common house bulbs, it's not working at the specified voltage.