Lā Ilāha Illallāh لا إله إلا الله A Statement Light On The Tongue But Heavy On The Scales -

Lā ilāha لا اله :
"I reject all false deities other than Allah to be worshipped"

Illa Allāh الا الله :
"I affirm that Allah alone is rightfully to be worshipped sincerely"

Allah said:

قُلِ ٱللَّهَ أَعْبُدُ مُخْلِصًا لَّهُۥ دِينِى

"Allah Alone I worship, sincerely for His sake in my religion [Islam]"

[Az-Zumar : 14]

All Prophets and Messengers were commanded to worship One God, Allah alone and they called their people to Worship Allah alone [AT-TAUHID]

Solat [prayers], Du'a [supplications], Istighathah [seeking aid], Dhabh [sacrificing animals] and all other acts of worship is for Allah alone and must not be directed to other than Allah.

Be aware of Shirk [WORST MAJOR SIN] - Directing any act of worship, small or big, to other than Allah.

Fear Allah and remember Him with your heart and tongue, repent to him as He loves you, He created you from nothing and you will return to Him.