PRAGUE, May 14 (Reuters) - German media group ProSiebenSat.1 should forge ahead with selling its e-commerce and online dating ventures, worth potentially over a billion euros, and invest more in content, the CEO of its second-largest shareholder said on Tuesday.

Czech investment group PPF is ProSieben's second largest shareholder with a 15% stake, after Italy's MFE-MediaForEurope with nearly 30%. MFE's proposal for ProSieben to spin off the e-commerce and online dating businesses narrowly failed in a shareholder vote in April.

PPF CEO Juri Smejc said his company has told ProSieben's management that it needs to refocus on content.

"The business certainly needs overhauling to refocus on content creation," Smejc told reporters.

"The company was not optimally managed for a long time. The company's potential is much bigger than the numbers are showing today."

Smejc said that PPF acted strictly independently of MFE, and did not share all MFE's positions.

"When it comes to the company's split, we think that those assets should be sold. Perhaps unlike shareholders at MFE, we do not have the feeling that it needs to be done in panic, for it to be sold next month, but it needs to be properly prepared."

He said it was right that ProSieben has started cutting costs, and it needs to invest more into content, including subscription video on demand, where he said ProSieben had "missed the boat".

Smejc said he could imagine PPF potentially taking a larger stake in ProSieben.

"It depends on the development of the share price and on how management succeeds in overhauling the firm," he said.

PPF owns the CME television business that has stations in six central and eastern European countries with 49 million viewers, and has pushed ahead with video on demand services. It has also acquired a 29.33% stake in Swedish streaming group Viaplay.

The group, owned by the family of deceased founder Petr Kellner, has been shifting interest away from Asia and Russia to Western markets, a trend represented by the ProSieben stake and which PPF aims to continue. (Reporting by Jan Lopatka Editing by Tomasz Janowski)