I have a LCD SAMSUNG LE32B450C4H. None of the controls are available to adjust contratst, luminosity, sound, ... What can I do?

The problem sounds related with its energy recovery circuit. Check this link for more details about these kind of fault.

From the samsung Answer in "How to adjust the brightness on your LED Monitor", There is written on the LIMITATION
Limitations:
This menu is not available when Samsung Magic Bright is set to Dynamic Contrast.
This menu is not available when Eco Saving Plus is set.
This menu is not available when Eye Saver Mode is enabled.
So with those condition matched, This menu(menu for adjustment) will not be available.

UPDATE WITH SOLUTION:
For windows user samsung is only giving link up to windows 7. For windows 8,10 use magicTune lite instead of magicTune premium.

Link for magicTune lite:
http://www.techplusme.com/software/download-samsung-magictune-widnows-8-1

UPDATED 2021-05-06
Above link is not working so adding new working link
https://magictunelitemain.software.informer.com/1.0/

Often manufactures will tie backlight adjustment in with the brightness, You might want to changed the brightness to your desired luminosity and then correct the picture with contrast to your liking.

Go online and visit Samsung website & search your device to see any available downloads or upgrades.

Need to get warranty service,
It seems not a big problem.
need to check the s/w & related cable on the TV.

It's your main control panel, most of the time they are not worth repairing.

adjust your dvd by using your remote control..adjust the volume control,and set them through menu,if not working your audio ic is deffective.

Go to the samsung website, and find out how to upgrade the firmware for your TV. You will probably need a portable usb memory stick to do so (if your TV is equipped with one). HDMI is an evolving technology, and firmware upgrades can resolve many of these quirky issues.

Here's a possibility from http://www.samsung.com/us/support/faqs/supportFaqList.do?group=&type=&subtype=&model_nm=LN-S4696D&dType=D&mType=UM&vType=R&prd_ia_cd=02010100&acc_ia_fl=&disp_nm=LN-S4696D
Which Samsung LCD TVs Have The HDMI 1.3 Interface? Of the LN-T series Samsung LCD TVs, those models whose last two digits are 61, 65, 66, 69, 71, or 81 (for example, LN-T4071F or LN-T466F) have the HDMI 1.3 interface.
Samsung LCD TVs with HDMI 1.3 interfaces also have HDMI-CEC (HDMI - Consumer Electronics Control). For information about CEC, click HERE.
For information about individual Samsung LCD TVs with HDMI 1.3 interfaces and HDMI-CEC, click HERE. When the Samsung LCD TV web page appears, select the TV model you want information about by clicking the drop down list under Product Finder on the left side of the page.
Though other series of Samsung LCD TVs (LN-R, LN-S, etc.) have HDMI connections, none have models with the HDMI 1.3 interface.

Defective lcd controller board. If the repair company and you are willing to wait less that 400 dollar repair. If not You are looking at having to replace a panel time to throw it away. The Lcd Controller board is available for this model.

Thanks
Josh

Usually the power supply is bad. Just 3 capacitors 1000uF 35volt rating. The 3 electrolytic caps will be puffed out, simply replace tham and you will be back in business.