Help a n00b root his spg512 xperia z2 tablet!

Ok so i have a xperia z2 tablet spg512 i need help to root it seems.

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Current state of tablet: stock rom,stock recovery,unlocked bootloader i think? as least it was but i soft bricked it and flashed stock 4.4.4 in flashtool so maybe it relocked? anyone know?

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i tried to install twrp 2.8.7.0 but it won't boot. i heard about you need to flash another boot.img so i tried cm12 boot.img but it just soft bricked and i fixed it with flashtool. i just want crdroid on it. anyone can help me on whatsapp or hangouts? thx. also i know about rooting and have rooted alot of things also flashed ALOT of custom roms and recoveryies. but this confuses me.