Headlight lense dirty

Are the headlight lenses dirty or discolored? There is a cleaning kit you can get to clean discoloration. If it is a bulb issue it will most likely be a ground problem with the headlight circuit

Chances are, it's pitting on the outside of the lense, not the inside. The inside probably is clean UNLESS, the rubber boot covering the holes is missing. You'd have to pull the headlight out and off the truck and try and clean through the holes the bulbs go into.

Nope....like this!

They can be adjusted up/down. see picture for adjustment screw.
The headlight housing can leak and condensation will form inside and maybe stain the inside. It is very difficult to take the housing apart... do go there.
It's more likely that that outside of the headlight is discolored with age. There are kits available at parts stores to recondition the outside of the lense.
The bulbs will also get dimmer with age. I recommend Philips VisionPlus; 9006 for low beams. You can get a pair on Ebay for $20 or less. They'll be $40-50/pr at the parts store.
This headlight is the easiest I have ever seen to remove. The headlamp can be easily removed by pulling up on the two white strips about a half inch (??). Then wiggle and pull the assembly straight forward.

You cannot remove the lense. it is factory sealed. only access inside is by removing bulb from rear of the lamp assembly. Your problem is probably a degraded hazy lense and not the inside. have lenses cleaned by a detailer or shop that can do a lense restoration.
Good luck

Check the light fittings themselves, the reflectors and the lenses, that they are clean and not faded. Check the bulbs that they are not dirty or blackened inside and that the contacts are clean, both the bulb contacts and the connectors and lastly check that the earth wires on the headlight fittings are connected and secure on both the bulb connectors and on the vehicle bodywork.

they are NOT detachable,if they are showing signs of flaking(streakes)you will have to replace them.....

You don't really remove the Headlight lenses unless you want to remove the front fenders. There are kits sold at most auto parts stores that you use to to clean the headlight lenses.

you cant really get inside of the lenses because they are glued together and usually break when you try to disassemble them. the lights should just turn slightly to the left and pull right out no special tools required.

At my shop we have a product from Ever-Wear, it is a headlight restoration kit, do it on the car and works great. Did one light on my car and left the other one foggy as a demo. Great Product