Do I understand correctly that Jesus Christ ascended to His Father after being resurrected, then returned to earth, and then ascended to heaven again?

Yes, you are correct. In John 20:17, Christ said to Mary, “Touch me not; for I am not yet ascended to my Father” (John 20:17). Then we see, a scant two verses later, in verse 19, that Jesus appeared that same day at evening in a locked room where the disciples were assembled, and showed them His pierced hands and side. Thus between the time Christ appeared to Mary and the time later that same evening, Christ had ascended up to His heavenly Father and returned. Eight days later, He appeared to the disciples again in a locked room with Thomas present (verse 26) and had Thomas thrust his finger into His wounded hands and his hand into His side. Jesus was with them for only 40 more days, and then He ascended again to the Father (Acts 1:3–11), where He awaits His second coming.