Samsung Galaxy Tab S2 in bootloop (standard recovery not working!) Hi enthusiastic community! I would need your help and advice!

The device:


Samsung Galaxy Tab S2 (SM-T819)
bought with Android 6 second hand --> last week updated to Android 7
NOT rooted, original firmware, official update (did not mess around with it at all ...)
I am using it without SD-card or SIM


The problem:

Stucks in boot loop first shows Galaxy Tab S2 logo and then S-A-M-S-U-N-G appears in big letters blinking) stays there forever and heat up a little on the back.

Steps already tried and did not work out:


press powerOn button 10s, 1 min, 2 min ... --> no reaction
press volUp + volDown + powerOn --> reboots put stuck later at the logo
press volUp + powerOn + home --> does not enter recovery mode 
press volDown + powerOn + home, in this very order --> enters downloading mode and asks to downloading a custom OS (volUp) or cancel (volDown)
if I press cancel reboots and stuck at the logo again
if volUp then gets into Odin downloading mode and shows the following information:

ODIN MODE (HIGH SPEED)
PROCUCT NAME: SM-T819
CURRENT BINARY: Samsung Official
SYSTEM STATUS: Official
FAP LOCKS: ON
WARRANTY VOID: 0x0
QUALCOMM SECUREBOOT: ENABLE (CSB)
RP SWREV: S1, T1, H1, R1, A2, P1
SECURE DOWNLOAD : ENABLE
download mode !!

[Arrow down]
Downloading ...
Do not turn off target 



I guess it is waiting to download from USB.


tried this steps with and without charging cable connected to my
laptop --> does not make a difference!
Eventually it ran out of battery and shut down! Tried the same
steps after it's shutdown (power cable connected) but situation did not change!
I cannot mount the tablet on my Ubuntu Lenovo Thinkpad --> if I do
lsusb the tablet is not listed ...
after the battery ran out I tried this: when Samsung Galaxy S2 logo appears, release the Power key and immediately hold the volume down key --> it is rebooting and showing the battery symbol (0% charged) over and over again.


Questions:


What should I do else? 
Should I flash firmware? --> I run the laptop with Ubuntu 17
Should I dismantle it and disconnect the battery (worked
on my Lenovo ...)? 
Do I have to root it?


What do I want:

I want the tablet to work again, would prefer not to root it, do not care about data loss ...

Other observations:


I could not start it this morning after installing a new app (via
Google Play) yesterday evening.   
Two days ago I could not charge the tablet with the adapter on a
power plug, I needed to charge it via the laptop.
It is alive and charges normally on the laptop (if I press shortly the powerOn button then the battery symbol appears)
Does NOT charge with the charger plugged into a power plug, only on the laptop.


Thanks a lot for your help and patience to read all that!

EDIT:

07/13/2017

I followed esQmo_'s solution in detail but I could not establish a connection between the computer and the tablet. In the end Samsung support fixed it and the tablet is running perfectly again. However, I think that the solution given by esQmo_ is still the right thing to do in this case, but please note that for some reason (maybe my lack of experience or knowledge) it did not work out for me. Thanks!
Seems like a softbrick state. You should try flashing a new firmware.
The steps below are for Windows:


Download the firmware from here (Registration required)
Download Odin flasher from here
Download Samsung Kies and install it. Needed for drivers.


[Update] 


Uninstall Kies right after it has installed and drivers set up, this is to avoid conflicts with Odin while flashing devices (See below answer (@Babaks D's answer) for more)
Unzip the firmware, unzip Odin then run the executable file.
Power off the device then boot in download mode (Volume down + power button) then connect it via USB cable. Windows should install drivers.
Now on Odin, you should see ID COM turns blue meaning that the device is detected.
Click on AP button, then browse where the firmware folder is. Select the file. Wait a moment.
Now click on Start and wait till the end. You should see PASS on the screen.