My wheel shows ETRO 622 * 19. The tire on it is 700*38c. I want to change tire and tube such that the bike becomes capable for 50% road bike and 50% off road. What size of tires and tube should i choose? Also, is it actually possible to do so or not?
With a 19 mm wide rim, your wheel will fit tyres from 28-44 mm wide (see Sheldon Brown tyre compatibility). You will also need to check the tyre clearance of your frame if you want to fit a larger tyre than the one you have now.
As for making your bike capable for 50% road and 50% off-road, you may not necessarily want to go with a wider tyre anyway. You will need to tell us what your current tyres are and what is wrong with them for us to help you with that decision.
I'll first answer your 2nd question.
Also, is it actually possible to do so or not?
With a 19 mm internal rim width, yes it is possible as long as you don't go too wide (like a 50 mm). Also, if your rims have Schrader (car valve) holes and you use Schrader-valve tubes, I suggest you shim your valve hole and use tubes with Presta valves instead to create more clearance in the rim, as forcing Shrader-valve tubes in that rim can strain the valve's base. You don't want to have a puncture right on the foot of your tube's valve.
What size of tires and tube should i choose?
From a cyclocross/gravel perspective, your tire size is sufficient enough but seeing as you're looking for better tires, I assume that the ones you have are too slick for off-road use.
If you're looking for size range, I suggest having tire width between 35-45 mm. Narrower tires are more aerodynamic and (semi-anecdotal) can be faster-rolling, while wider tires offer better grip.
Get tires with sufficient tread/knobbles. Side knobbles also help in cornering off-road. Refer to my answer in this link for CX/gravel tire tread comparison: Replacement for discontinued Schwalbe Tyrago
Finally, the tube size. While I would recommend you convert to tubeless system if you're using that bike for 50% offroad, it's okay if you use tubes. If you do, I'll share some anecdotal advice: Use inner tubes that are one size/step larger than your tire, and by that I mean width, not diameter.
I find that oversizing inner tubes helps with punctures as the tube doesn't have to stretch as far in order to fill the tire, so the tube wall is 'meatier' and most likely more puncture-resistant. Snakebite/pinch punctures won't help you much though.