Walta started at HJK Helsinki when he was eight years old.[1] Walta was a very attractive player during his youth years at HJK, where it led to several trials in, among others, German clubs TSG 1899 Hoffenheim and Bayern Munich, and also at Dutch club PSV Eindhoven.[2] However, he couldn't move abroad until he was 16 years old, according to FIFA rules.
Therefore, he stayed at HJK and at the age of 15 in May 2019, started playing for HJK's reserve team, Klubi 04, in the Finnish third division, Kakkonen.[3]
FC Nordsjælland
In September 2019 it was announced, that FC Nordsjælland had bought 16-year old Walta from HJK Helsinki for "a significant transfer amount".[1] In his first season at the club, he mostly played for the U-17 team, but also made seven appearances and scored two goals for the U-19s, while he also made his reserve team debut in November 2019.
In the 2020–21 season, Walta became a key player for Nordsjælland's U19s, where he played 23 league games and scored six goals. At the end of the season, on 14 July 2021, Nordsjælland confirmed, that Walta had signed a new deal with the club and had been promoted to the first team squad.[4] Four days later, on 18 July 2021, Walta got his professional debut for Nordsjælland against Viborg FF in the Danish Superliga.[5]
HB Køge (loan)
On transfer deadline day, 31 January 2023, HB Køge confirmed that Walta had joined the club on a loan deal for the remainder of the season.[6]
Mjällby AIF (loan)
After returning to Nordsjælland, he was sent out on loan again, this time to Allsvenskan club Mjällby AIF until the end of the 2023 season.[7] On 18 September 2023, Walta scored his first goals in Allsvenskan by a brace against IFK Norrköping away, helping his side to take a 2–0 win.[8][9] After the season, Mjällby were interested in signing with Walta on a permanent contract, but Nordsjælland's asking price of €1.3 million was too high for them. It was also reported that there were several interested clubs in Eredivisie.[10]
IK Sirius
On 8 March 2024, Walta joined Allsvenskan side Sirius on a deal until 30 June 2028 for an undisclosed fee, reported to be €1.25 million.[11][12]
International career
Walta is a regular youth international, and has represented Finland at various youth national team levels.
On 4 June 2024, Walta made his senior national team debut for Finland, in a 4–2 friendly defeat against Portugal.[13]