Peppers are perennial in hot climates so they should keep going and produce well as long as there is enough light.

Thank you,

and another question is how to strengthen the stem?

I see a lot of YouTubers videos with strong and thick stem yet mine is "thin", right now the branches leaning toward the wall for support otherwise they'll fall down...

The plant is probably weak because you appear to be growing it inside like a houseplant, which is challenging. Can you set it outside during the Summer? If you are just growing it near a window with no other options I would not expect much from the plant long term. You could trim the weak branches off and see if it makes new growth, but probably not worth saving as a houseplant.

well, thanks for the answers.

I am thinking about getting a growing lights... do I need to look for specific data of the light?

Edit- the vegetables I am planning to have are potatoes, tomatoes, cucumbers and peppers (chili and sweat)

If the plant is big enough to lean and need support. Give it support. Many pepper plants benefit from having support. You can do things like a couple centeral stakes to support the central stem, or get a small tomato cage so the branches can get supported as they need to and the cage keeps the plant in general supported.

Also, how old is your pepper plant? Is this the first flush of fruit, do you have more blossom buds forming? If your plant is early on in maturity and starting it's first set of fruit, great! But keep in mind that even if you grow them like perennials, peppers still need a bit of resting time between flowering and fruiting times, just like most other perennials.

Thanks for the reply.

So I am planning to get growing led lights (really can't grow outside- cold country).

How can I know how much is ok?

So far I saw for 7w bulb red color: 620-630nm, blue color: 455-460nm.

As well is it enough to plug-in the bulb in regular ikea stand or should I buy specific one for growing lights?

Can't really tell you if an Ikea stand will be good or not. The stand should say what it's maximum output is- usually in the bulb socket. You might need a stand meant for grow lights.

Personally I use LED grow panels, small ones. Others often use shop lights, and I've also used them in the past. I use my lights for seed starting and micro growing, not for year round lighting of plants.