While reading "Tithing is Unscriptural Under the New Testament Parts I and II" (great article by the way) I noticed this Scripture
And thither ye shall bring your burnt offerings, and your sacrifices, and your TITHES, and heave offerings of your hand, and your vows, and your freewill offerings and the firstlings of your herds and of your flocks: And there ye shall eat before the Lord your God, and ye shall rejoice in all that ye put your hand unto, YE and YOUR HOUSEHOLDS, wherein the Lord thy God hath blessed thee
Deut. 12:6-7
I bolded intentionally the word "freewill". We all know that there is no free will at all, so I started worrying if this is a contradiction. Suddenly it came to me (by God's spirit, he?) that maybe we should understand this "freewill" as not being forced to give those offerings by somebody else. Is my reasoning is correct in this matter? Or am I wrong? Thank you in advance for you reply.
May God keep you in his care, brothers and sisters 
Yes, that is correct Dawidos. The freewill offering was voluntary, and not obligated by the Lord.
On the topic of free will, most people that I have encountered do not believe all will be saved because God will not 'force' people to love and obey Him. But God does 'inspire' us to voluntarily love and obey Him, just by His Love & Grace.
It's that last statement that just leaves these same people shaking their heads. They won't believe until they see it....but they WILL believe it.

Marques