When the tree is young it needs to be in a small container and then upsized as it grows. Putting it in a container too large for the tree often leads to root rot.

I don’t think rootrot is a big issue where you are. Sometimes when you buy a tree, it might be ready for 5 or 7gl pot. But if you have a 10gl pot, you don’t have to fill it to the top. You can start half way and fill higher after 2 or 3 years.

Both, both great answers!

As for what kind?

Clay is best for anyone who tends to over water or use a mix that is too water retentive.

Anything that holds a plant is great from plastic, tin, wood, buckets, acrylic, resin, anything you get your hands on that will hold a mix. Just make sure you know how to water and what kind of mix to use accordingly and that all containers have holes at the bottom.

Mike

Thank you for the answers But do the lemon trees mind living in the heat of my summers? the temperatures reach up to 115 degrees Fahrenheit if not more, And what is better from protecting it fro mother heat, spraying the leaves with organic paint, putting a shade cloth, or simply giving it less sunlight to reduce the heat

Most likely meant trunk, painting the leaves would kill the tree as photosynthesis would not be able to happen.

The reason why I said spray the leaves with white organic spray I would have maybe put a little bit and the white will reflect the heat so that the leaves won’t burnt and become brown

I would like to hear from people in South Texas and around Phoenix Arizona on all this. I mean that is serious HEAT. LOL! You'll probably have to shade plants through much of your summer. And give them more sun as you get into your 'cooler' months. As long as you shade the plants they may be OK. I would select a pot that is light in color - or perhaps paint it white. Perhaps a styrofoam-type insulated pot.

but it is even in the few hundreds even in the shade sometimes and it is really humid and if I give it for example 4 hours of sun from that will it be equal to 8 hours of sun in the cooler months

there is a horticultural product (kaolin clay) that is used for sunburn

http://citrusindustry.net/2019/10/02/a-growth-enhancing-pest-management-option/

I think you will be best with a final pot size of 15 gallons, or more. Select a light color or paint it.

Also take note of the reflective surfaces where you want to grow.

the thing is that I live in Doha Qatar and idk where to get them