Romelu Lukaku celebrates scoring for Everton 1 Striker Romelu Lukaku appears to have learned from his previous experience under Jose Mourinho after admitting he will have to “work harder than ever before” when his move to Manchester United is confirmed.The Belgium international is on the verge of completing a potential world-record move to Old Trafford, with the Red Devils paying an initial £75million plus several add-ons.It will reunite him with United boss Mourinho, the man who sold him as a raw 21-year-old at Chelsea after just 15 matches and no goals.Lukaku has improved significantly since then, scoring 33 Premier League goals in his last two seasons at Goodison Park, but knows he will have to go up another level under the Portuguese at United.“Now it’s time to work hard, work harder than I ever did before and I’m willing to do it and hopefully it will come (off) a good way,” he told ESPN after it was announced United had reached an agreement with Everton on Saturday.Asked about joining United, he said that the club had “probably the best manager in the world”.“(The club are managed by) A guy who I wanted to play for since I was 10 years old so now to have an opportunity to play under him again is great,” he added.“I have to work harder than I am doing now and I know the road is still far but I am willing to go on that path and grab that opportunity that I get.“It’s the biggest club in the world. It’s a club that’s hungry to win the league again, to be dominant in the world again.“This is the sort of opportunity that I always wanted since I was a child and when they came calling, I didn’t have to think twice.“I’m really delighted to hopefully be part of their history. Who would say no to the biggest club in the world? The best stadium in England, the best fans, it’s the perfect opportunity.“I always said that I wanted to play for a team that was challenging for every trophy that there is, and I think Manchester United at the minute wants to be that dominant team, that dominant force.“And if you look at their history it says enough and to become part of a club like them is something that I really wanted, and I’m thankful for the opportunity that they gave me.”Lukaku is set to join up with his new team-mates on Monday when they land in Los Angeles, where the Belgian has been holidaying with close friend and new team-mate Paul Pogba. United begin their 18-day pre-season tour from there which includes friendlies with Los Angeles Galaxy and Real Salt Lake, plus matches against Manchester City, Barcelona and Real Madrid in the International Champions Cup.Lukaku appeared to confirm reports he had already undergone his medical with United in a series of posts on his Instagram account.The 24-year-old posted a picture of him with the words “Medicals…” before further images and text saying “When u waiting for the next check up…” and “On to the next one…”The next picture was of a bare-chested Lukaku lying down with what appeared to be electrodes attached to his torso, accompanied by the words: “Please come save me”Lukaku then posted a picture of him signing the Manchester United shirt of a young fan, with the striker saying “First Manchester United fan i’ve met..#Blessed #Thankful”.He finished off with a picture of him giving the camera a thumbs up with the word “Finito”.