If you have faith as a mustard seed, you will say to this mountain

Matthew 17:20
So Jesus said to them, “Because of your unbelief;[d] for assuredly, I say to you, if you have faith as a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible for you.

In our initial walk with God, our little faith can more often been rewarded by confirmation from God. As we mature, God expects us to walk in stronger faith with Him and no longer need Him to show miraculous things. There will be trials of faith where we are put to the tests, and then there is also ordinary life itself which is usually a challenge to our faith because the natural world is different from God's world. Job is a good example of strength in faith - Job 13:15 - though He slay me, yet I will trust Him.

Without faith, it is impossible to please God

Hebrews 11:6
Without faith, it is impossible to please God.

Faith and commonsense are different dimensions and are not strictly exclusive to each other. One can exercise faith and still use common sense to test the faith revelations. Some things that Yshua reveals to us does not always make (common) sense, but there are some revelations that need to be tested. Faith itself is not based on reasoning but is based on the person of Yshua. We trust Him, and so we obey His commands, and believe what He says is true.

For He made Him who knew no sin to be sin for us

2 Corinthians 5:21
For He made Him who knew no sin to be sin for us, that we might become the righteousness of God in Him.

It was God the Father's will that the Son Yshua went to the cross and paid the price of since for mankind. Yshua obeyed His Father's will and went to the cross. We are saved because of what He has done and by obeying Him as our Lord. Those who chose not to believe are still living in disobedience and hence are not saved.

We were reconciled to God through the death of His Son

Romans 5:10
For if when we were enemies we were reconciled to God through the death of His Son, much more, having been reconciled, we shall be saved by His life.

Our salvation is totally the result of Yshua sacrificing Himself on the cross and shedding His blood for us. From terminology sometimes such as need for repentance to be saved and so on, there is a danger that makes us think we have to do something and that leads to our salvation. Atonement has been accomplished for us, it does not depend on what we do including the act of following Messiah.

Go therefore and make disciples of all the nations

Matthew 28:19
Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit

Making disciples can be understood in the following way. Usually we think this verse means to tell the gospel with the intention of converting others. However, to make disciples may also mean that the seed has sown, and that the people have already been converted to Christ by the supernatural work of the Holy Spirit. At that stage, they will be like newborn babes. God as the Father would want to see these new Christians being cared for, hence the making of disciples could well mean grooming new Christians by bringing them into lifelong discipleship of our Lord Yshua.

As the Father has sent Me, I also send you

John 20:21
So Jesus said to them again, “Peace to you! As the Father has sent Me, I also send you.”

Missionary work is about obeying Jesus because He is the one who send us. He goes behind all those who carry out the work of God. It is important to be mindful that we are working for Jesus, and not about how successful we can win souls. It requires childlike obedience in general to follow the Lord and doing His work is no different. No matter how urgent the needs of others are, we cannot afford to forget the Lord.

I have become all things to all men

1 Corinthians 9:22
to the weak I became as[f] weak, that I might win the weak. I have become all things to all men, that I might by all means save some.

Paul has given himself totally to serving God. There was no prejudice in him nor choosing the way he wanted to serve God. He did not plan to preach to a certain group of people, in fact he would have preferred to preach to his own people, but God had appointed him to preach to the Gentiles. So as God calls us, all we need is to obey, instead of telling God to bless us once we have made all the plans for ministry.