God an be made out to be a liar, if someone translates His words in such a way as to make Him seem a liar.
Do a word search on "surely" and you will find plenty of examples where the outcome is predicted and was not immediately effected but was gradually brought to pass. Some have Been taught the doctrine of original sin, and are needing to post hoc rationalise their belief in original sin. To do so, they enlist this verse, claiming it says death will immediately come to pass, and therefore the death referred to cannot be not physical death, so must be spiritual death, separation from God. They then apply this "separation from God kind of death" to all Adam's descendants, even in the womb, and so prove to their own satisfaction, but not to mine, that original sin is a real thing.
Here are some texts that use the structure "infinitive absolute verb form + imperfective verb form pair" that are describing a gradual outcome, not an immediate outcome.
Gen 28:22 And this stone, which I have set
for a pillar, shall be God's house: and of all that thou shalt give me
( עַשֵּׂר אֲעַשְּׂרֶנּוּ , infinitive absolute + imperfective piel) unto thee.
Gen 32:12 And thou saidst,
I will surely do ( הֵיטֵב אֵיטִיב , infinitive absolute + imperfective hiphil) thee good, and make thy seed as the sand of the sea, which cannot be numbered for multitude.
Gen 50:24 And Joseph said unto his brethren, I die: and
God will surely visit ( פָּקֹד יִפְקֹד , imperfective Qal + infinitive absolute.) you, and bring you out of this land unto the land which he sware to Abraham, to Isaac, and to Jacob.
There are many others. You can do the word search yourself, if you are interested in the truth.