1) Consider "app development" as a single competence

Error: Assume that every agency that "makes apps" covers native iOS/Android, cross-platform, web apps, APIs, analytics and security in equal measure.
Solution: Architectural skills couple. A credible partner shows depth in native and cross-platform (e.g. React Native), web app delivery and back-end/API work - and explains when which choice wins on UX, performance or TCO. Use published native, web and API services to explore real projects and trade-offs.

2) Skip discovery/feasibility

Error: "We know the scope - just build it." This creates misguided features and late cost leaps.
Solution: A short Discovery + feasibility (requirements, risks, data, KPIs) and cut an MVP. Published cost corridors (e.g. MVPs from ~12 k€; medium-sized apps 20-60 k€) are helpful as a planning baseline to manage phases and expectations.

3) Select by price tag only

Error: Lowest bid wins, with unclear content (QA, CI/CD, analytics, store handling, warranty).
Solution: Total cost of ownership compare. Ask what is included in each phase (build, hardening, operation). A model with German PM and Indian engineering capability can deliver good value for money - without reliability and communication quality. References and SLAs must prove this.

4) Do not check results (portfolios only)

Error: Focusing on shiny decks instead of Production results leave
Solution: Ask for real systems, constraints and outcomes. Example: PUMA CATchup - an employee content app where native mobile apps were delivered to a global workforce and stakeholders; review how content systems, notifications and analytics were integrated.

5) Underestimate integrations

Error: "We'll connect ERP/CRM/S3/Sage later." Integrations routinely represent 50-70 % of time risk.
Solution: Pattern for Auth, retries, idempotency, versioning and data contracts. Ensure that API work is a first-class service, not an afterthought.

6) Ignore analytics, monitoring and release hygiene

Error: Launch without crash monitoring, logging, funnel analytics and release checklists.
Solution: Operational readiness demand: Crash/error targets, analytics events with data dictionary, staging/prod parity and rollback plans. Verify how similar production apps are operated (e.g. how content pipelines have been monitored and tuned over time).

7) Unclear code/IP ownership and handover

Error: Contracts that Source code, infra-as-code, designs and documentation not clearly transferred.
Solution: Make IP assignment explicit. Require repo access at every milestone, runbooks and handover workshops. Confirm NDA, data handling and GDPR-compliant processes in writing.

8) Treat GDPR & security as an end-phase add-on

Error: "We do privacy/security at the end."
Solution: Privacy-by-Design from day 1: data minimization, consent flows, role-based access, encryption in transit/at rest and vendor DPAs. Ask for interpretation for German/EU data residency and audits. Agree specific controls and checklists.

9) No product management cadence

Error: No stable rhythm for demos, acceptance criteria, change requests (CRs) and escalation.
Solution: Sprint reviews, clear Definition of DoneCR workflow (thresholds and SLAs) and a responsible product owner on your side.

10) Overlook maintainability

Error: Deliver a build that only the vendor can change.
Solution: CI/CDtest coverage reports, environment diagrams and dependency inventories. Prefer mainstream stacks (Swift/Kotlin or React Native + Node/Java/.NET) and insist on a warranty window.