I was wondering if we could lose our salvation by sinning, then does that make it a works salvation? In order to keep our salvation we would have to do good works, but salvation is not based on works, right? (Eph. 2:8-9) Also if God said that He would give us eternal life (John 10:28) when we are saved, and if we can lose it, then does that mean that God has lied to us? Salvation is a gift from God and he will not take back those gifts that He has given to us including eternal life. (Rom 11:29) Tell me what you think of these questions and comments.
To answer your questions: no, yes and no, no. And to your final comment: that’s not what the verse says. Now for the detail.
First, you base your questions on a faulty premise. One does not lose their salvation by sinning, per se, but by turning their back on the gift God has given. I get a lot of questions in the format, “If I do [whatever sin they are asking about], will I go to hell?” My usual answer is along the lines that one sin will result in you going to hell if you have not put on Christ, but once you are in Christ one sin will not cause you to lose your salvation. It’s sort of like if you are married and you cheat on your wife, that doesn’t cancel the marriage. If, on the other hand, you divorce your wife, then the marriage is cancelled.
Even if the Bible taught that one sin could cause you to lose your salvation, that would not necessarily make it a works salvation. Does the fact that most Baptists I know say that you have to believe and pray “the sinner’s prayer” mean that they believe in a “works salvation?” They would deny that. Because we can and will continue sinning, even after we receive salvation, that doesn’t negate that the salvation is God’s gift. Because we have a new life, we don’t continue to live the old life of sin (Romans 6). It is no longer that we practice sinning, or choose to live a life that is based on sin. Paul says that life is dead; after we are buried in baptism we walk in a new life. But he also says that even he sometimes does what he doesn’t want to do (Romans 7). So the answer to your first question is no.
You refer to Ephesians 2:8-9 to say that salvation is not based on works. You have to remember that in Galatians and Ephesians Paul uses the word “works” as a shorthand for “works of law” or legalism. What he is telling the Christians in those places (and us through them) is that even under the Law of Moses one was not saved merely by keeping the law perfectly. Because God demands the service of the heart, even if one kept the letter of the law, he still would be in violation if he did it our of a slavish sense of “I don’t want to, but I have to.” “For the whole law is fulfilled in one word, even this: Thou shalt love thy neighbor as thyself.” (Galatians 5:14) In other words, if you don’t have love, you violate the law just as much, even if you fulfill every other provision. So Paul was not telling the Ephesians that salvation is not based on right actions. He is telling them it is not based on legalism, the idea that I can earn my own salvation. Thus the answer to your second question is yes and no.
The third question asks whether losing one’s salvation (what Paul calls falling from grace in Galatians 5:4) would make God a liar. Emphatically, no! All God’s promises have always been conditional on our following Him. This is even emphasized in the passage to which you refer, John 10:28. Jesus says his sheep hear his voice, and he will give them eternal life and no one will be able to snatch them out of his hand. Look at the sheep. While he is following the shepherd he is safe. No wolf can come and take the sheep. But if the sheep wanders away from the shepherd, the shepherd can no longer protect it. No one can snatch it, but it can leave of its own accord. That is why Paul told the Galatians that relying on legalism means they have fallen from grace. They are no longer relying on the grace of God for salvation, and so they have turned their back on God. If we walk away from God, that doesn’t make him a liar. That just makes us guilty.
Finally, you say God “will not take back those gifts that He has given to us including eternal life. (Rom 11:29)” God gave Israel a land, but when they turned their back on him he took the land away. (Read Jeremiah and several of the Minor Prophets on that.) God gave Adam and Eve a place to live, but took it away from them when they ate of the forbidden tree. Nevertheless, that is not what the scripture says. The passage says, “The gifts and calling of God are without repentance.” Some versions mistranslate that to say they are “irrevocable,” even though the Greek word used never has that meaning. (This would seem to indicate that those versions translate it that way because they want to prove something that is not otherwise scriptural.) The context of the passage is not individual salvation, but God’s choosing of Israel and the fact that they, too, can be saved even though salvation was opened to the Gentiles. What verse 29 is saying is that God’s choosing of non-Jews does not mean he is sorry he chose the Jews in the first place. He didn’t repent his first choosing and calling. He just expanded it. As with much of the book of Romans, Paul is not referring to individuals but to the contrast between Jews and non-Jews. It’s the same misinterpretation that makes people think that the “all” of Romans 3:23 (“All have sinned and come short of the glory of God.”) means all individuals instead of both Jews and non-Jews. God isn’t going to reject the Jews just because he accepted the Gentiles. That is what the verse means. To make it mean anything else is to tear it out of context. It has nothing to do with whether one can lose one’s salvation. There are about 200 other verses that say it is possible, and the Bible doesn’t contradict itself.